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c31ad71f10
Building against shared libraries only implemented for Linux X11 so far. TODO: Document Godot's modifications of upstream enet.
654 lines
21 KiB
C
654 lines
21 KiB
C
/**
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@file compress.c
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@brief An adaptive order-2 PPM range coder
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*/
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#define ENET_BUILDING_LIB 1
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#include <string.h>
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#include "enet/enet.h"
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typedef struct _ENetSymbol
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{
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/* binary indexed tree of symbols */
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enet_uint8 value;
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enet_uint8 count;
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enet_uint16 under;
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enet_uint16 left, right;
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/* context defined by this symbol */
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enet_uint16 symbols;
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enet_uint16 escapes;
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enet_uint16 total;
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enet_uint16 parent;
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} ENetSymbol;
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/* adaptation constants tuned aggressively for small packet sizes rather than large file compression */
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enum
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{
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ENET_RANGE_CODER_TOP = 1<<24,
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ENET_RANGE_CODER_BOTTOM = 1<<16,
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ENET_CONTEXT_SYMBOL_DELTA = 3,
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ENET_CONTEXT_SYMBOL_MINIMUM = 1,
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ENET_CONTEXT_ESCAPE_MINIMUM = 1,
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ENET_SUBCONTEXT_ORDER = 2,
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ENET_SUBCONTEXT_SYMBOL_DELTA = 2,
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ENET_SUBCONTEXT_ESCAPE_DELTA = 5
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};
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/* context exclusion roughly halves compression speed, so disable for now */
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#undef ENET_CONTEXT_EXCLUSION
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typedef struct _ENetRangeCoder
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{
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/* only allocate enough symbols for reasonable MTUs, would need to be larger for large file compression */
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ENetSymbol symbols[4096];
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} ENetRangeCoder;
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void *
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enet_range_coder_create (void)
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{
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ENetRangeCoder * rangeCoder = (ENetRangeCoder *) enet_malloc (sizeof (ENetRangeCoder));
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if (rangeCoder == NULL)
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return NULL;
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return rangeCoder;
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}
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void
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enet_range_coder_destroy (void * context)
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{
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ENetRangeCoder * rangeCoder = (ENetRangeCoder *) context;
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if (rangeCoder == NULL)
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return;
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enet_free (rangeCoder);
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}
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#define ENET_SYMBOL_CREATE(symbol, value_, count_) \
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{ \
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symbol = & rangeCoder -> symbols [nextSymbol ++]; \
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symbol -> value = value_; \
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symbol -> count = count_; \
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symbol -> under = count_; \
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symbol -> left = 0; \
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symbol -> right = 0; \
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symbol -> symbols = 0; \
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symbol -> escapes = 0; \
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symbol -> total = 0; \
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symbol -> parent = 0; \
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}
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#define ENET_CONTEXT_CREATE(context, escapes_, minimum) \
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{ \
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ENET_SYMBOL_CREATE (context, 0, 0); \
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(context) -> escapes = escapes_; \
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(context) -> total = escapes_ + 256*minimum; \
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(context) -> symbols = 0; \
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}
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static enet_uint16
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enet_symbol_rescale (ENetSymbol * symbol)
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{
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enet_uint16 total = 0;
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for (;;)
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{
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symbol -> count -= symbol->count >> 1;
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symbol -> under = symbol -> count;
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if (symbol -> left)
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symbol -> under += enet_symbol_rescale (symbol + symbol -> left);
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total += symbol -> under;
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if (! symbol -> right) break;
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symbol += symbol -> right;
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}
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return total;
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}
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#define ENET_CONTEXT_RESCALE(context, minimum) \
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{ \
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(context) -> total = (context) -> symbols ? enet_symbol_rescale ((context) + (context) -> symbols) : 0; \
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(context) -> escapes -= (context) -> escapes >> 1; \
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(context) -> total += (context) -> escapes + 256*minimum; \
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}
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#define ENET_RANGE_CODER_OUTPUT(value) \
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{ \
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if (outData >= outEnd) \
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return 0; \
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* outData ++ = value; \
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}
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#define ENET_RANGE_CODER_ENCODE(under, count, total) \
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{ \
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encodeRange /= (total); \
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encodeLow += (under) * encodeRange; \
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encodeRange *= (count); \
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for (;;) \
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{ \
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if((encodeLow ^ (encodeLow + encodeRange)) >= ENET_RANGE_CODER_TOP) \
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{ \
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if(encodeRange >= ENET_RANGE_CODER_BOTTOM) break; \
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encodeRange = -encodeLow & (ENET_RANGE_CODER_BOTTOM - 1); \
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} \
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ENET_RANGE_CODER_OUTPUT (encodeLow >> 24); \
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encodeRange <<= 8; \
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encodeLow <<= 8; \
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} \
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}
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#define ENET_RANGE_CODER_FLUSH \
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{ \
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while (encodeLow) \
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{ \
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ENET_RANGE_CODER_OUTPUT (encodeLow >> 24); \
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encodeLow <<= 8; \
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} \
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}
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#define ENET_RANGE_CODER_FREE_SYMBOLS \
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{ \
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if (nextSymbol >= sizeof (rangeCoder -> symbols) / sizeof (ENetSymbol) - ENET_SUBCONTEXT_ORDER ) \
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{ \
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nextSymbol = 0; \
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ENET_CONTEXT_CREATE (root, ENET_CONTEXT_ESCAPE_MINIMUM, ENET_CONTEXT_SYMBOL_MINIMUM); \
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predicted = 0; \
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order = 0; \
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} \
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}
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#define ENET_CONTEXT_ENCODE(context, symbol_, value_, under_, count_, update, minimum) \
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{ \
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under_ = value*minimum; \
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count_ = minimum; \
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if (! (context) -> symbols) \
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{ \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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(context) -> symbols = symbol_ - (context); \
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} \
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else \
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{ \
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ENetSymbol * node = (context) + (context) -> symbols; \
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for (;;) \
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{ \
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if (value_ < node -> value) \
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{ \
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node -> under += update; \
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if (node -> left) { node += node -> left; continue; } \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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node -> left = symbol_ - node; \
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} \
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else \
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if (value_ > node -> value) \
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{ \
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under_ += node -> under; \
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if (node -> right) { node += node -> right; continue; } \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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node -> right = symbol_ - node; \
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} \
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else \
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{ \
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count_ += node -> count; \
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under_ += node -> under - node -> count; \
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node -> under += update; \
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node -> count += update; \
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symbol_ = node; \
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} \
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break; \
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} \
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} \
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}
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#ifdef ENET_CONTEXT_EXCLUSION
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static const ENetSymbol emptyContext = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
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#define ENET_CONTEXT_WALK(context, body) \
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{ \
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const ENetSymbol * node = (context) + (context) -> symbols; \
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const ENetSymbol * stack [256]; \
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size_t stackSize = 0; \
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while (node -> left) \
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{ \
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stack [stackSize ++] = node; \
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node += node -> left; \
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} \
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for (;;) \
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{ \
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body; \
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if (node -> right) \
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{ \
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node += node -> right; \
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while (node -> left) \
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{ \
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stack [stackSize ++] = node; \
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node += node -> left; \
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} \
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} \
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else \
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if (stackSize <= 0) \
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break; \
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else \
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node = stack [-- stackSize]; \
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} \
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}
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#define ENET_CONTEXT_ENCODE_EXCLUDE(context, value_, under, total, minimum) \
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ENET_CONTEXT_WALK(context, { \
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if (node -> value != value_) \
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{ \
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enet_uint16 parentCount = rangeCoder -> symbols [node -> parent].count + minimum; \
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if (node -> value < value_) \
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under -= parentCount; \
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total -= parentCount; \
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} \
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})
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#endif
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size_t
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enet_range_coder_compress (void * context, const ENetBuffer * inBuffers, size_t inBufferCount, size_t inLimit, enet_uint8 * outData, size_t outLimit)
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{
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ENetRangeCoder * rangeCoder = (ENetRangeCoder *) context;
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enet_uint8 * outStart = outData, * outEnd = & outData [outLimit];
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const enet_uint8 * inData, * inEnd;
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enet_uint32 encodeLow = 0, encodeRange = ~0;
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ENetSymbol * root;
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enet_uint16 predicted = 0;
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size_t order = 0, nextSymbol = 0;
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if (rangeCoder == NULL || inBufferCount <= 0 || inLimit <= 0)
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return 0;
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inData = (const enet_uint8 *) inBuffers -> data;
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inEnd = & inData [inBuffers -> dataLength];
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inBuffers ++;
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inBufferCount --;
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ENET_CONTEXT_CREATE (root, ENET_CONTEXT_ESCAPE_MINIMUM, ENET_CONTEXT_SYMBOL_MINIMUM);
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for (;;)
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{
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ENetSymbol * subcontext, * symbol;
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#ifdef ENET_CONTEXT_EXCLUSION
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const ENetSymbol * childContext = & emptyContext;
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#endif
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enet_uint8 value;
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enet_uint16 count, under, * parent = & predicted, total;
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if (inData >= inEnd)
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{
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if (inBufferCount <= 0)
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break;
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inData = (const enet_uint8 *) inBuffers -> data;
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inEnd = & inData [inBuffers -> dataLength];
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inBuffers ++;
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inBufferCount --;
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}
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value = * inData ++;
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for (subcontext = & rangeCoder -> symbols [predicted];
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subcontext != root;
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#ifdef ENET_CONTEXT_EXCLUSION
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childContext = subcontext,
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#endif
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subcontext = & rangeCoder -> symbols [subcontext -> parent])
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{
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ENET_CONTEXT_ENCODE (subcontext, symbol, value, under, count, ENET_SUBCONTEXT_SYMBOL_DELTA, 0);
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* parent = symbol - rangeCoder -> symbols;
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parent = & symbol -> parent;
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total = subcontext -> total;
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#ifdef ENET_CONTEXT_EXCLUSION
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if (childContext -> total > ENET_SUBCONTEXT_SYMBOL_DELTA + ENET_SUBCONTEXT_ESCAPE_DELTA)
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ENET_CONTEXT_ENCODE_EXCLUDE (childContext, value, under, total, 0);
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#endif
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if (count > 0)
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{
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ENET_RANGE_CODER_ENCODE (subcontext -> escapes + under, count, total);
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}
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else
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{
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if (subcontext -> escapes > 0 && subcontext -> escapes < total)
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ENET_RANGE_CODER_ENCODE (0, subcontext -> escapes, total);
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subcontext -> escapes += ENET_SUBCONTEXT_ESCAPE_DELTA;
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subcontext -> total += ENET_SUBCONTEXT_ESCAPE_DELTA;
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}
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subcontext -> total += ENET_SUBCONTEXT_SYMBOL_DELTA;
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if (count > 0xFF - 2*ENET_SUBCONTEXT_SYMBOL_DELTA || subcontext -> total > ENET_RANGE_CODER_BOTTOM - 0x100)
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ENET_CONTEXT_RESCALE (subcontext, 0);
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if (count > 0) goto nextInput;
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}
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ENET_CONTEXT_ENCODE (root, symbol, value, under, count, ENET_CONTEXT_SYMBOL_DELTA, ENET_CONTEXT_SYMBOL_MINIMUM);
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* parent = symbol - rangeCoder -> symbols;
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parent = & symbol -> parent;
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total = root -> total;
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#ifdef ENET_CONTEXT_EXCLUSION
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if (childContext -> total > ENET_SUBCONTEXT_SYMBOL_DELTA + ENET_SUBCONTEXT_ESCAPE_DELTA)
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ENET_CONTEXT_ENCODE_EXCLUDE (childContext, value, under, total, ENET_CONTEXT_SYMBOL_MINIMUM);
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#endif
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ENET_RANGE_CODER_ENCODE (root -> escapes + under, count, total);
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root -> total += ENET_CONTEXT_SYMBOL_DELTA;
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if (count > 0xFF - 2*ENET_CONTEXT_SYMBOL_DELTA + ENET_CONTEXT_SYMBOL_MINIMUM || root -> total > ENET_RANGE_CODER_BOTTOM - 0x100)
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ENET_CONTEXT_RESCALE (root, ENET_CONTEXT_SYMBOL_MINIMUM);
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nextInput:
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if (order >= ENET_SUBCONTEXT_ORDER)
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predicted = rangeCoder -> symbols [predicted].parent;
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else
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order ++;
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ENET_RANGE_CODER_FREE_SYMBOLS;
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}
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ENET_RANGE_CODER_FLUSH;
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return (size_t) (outData - outStart);
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}
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#define ENET_RANGE_CODER_SEED \
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{ \
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if (inData < inEnd) decodeCode |= * inData ++ << 24; \
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if (inData < inEnd) decodeCode |= * inData ++ << 16; \
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if (inData < inEnd) decodeCode |= * inData ++ << 8; \
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if (inData < inEnd) decodeCode |= * inData ++; \
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}
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#define ENET_RANGE_CODER_READ(total) ((decodeCode - decodeLow) / (decodeRange /= (total)))
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#define ENET_RANGE_CODER_DECODE(under, count, total) \
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{ \
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decodeLow += (under) * decodeRange; \
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decodeRange *= (count); \
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for (;;) \
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{ \
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if((decodeLow ^ (decodeLow + decodeRange)) >= ENET_RANGE_CODER_TOP) \
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{ \
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if(decodeRange >= ENET_RANGE_CODER_BOTTOM) break; \
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decodeRange = -decodeLow & (ENET_RANGE_CODER_BOTTOM - 1); \
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} \
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decodeCode <<= 8; \
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if (inData < inEnd) \
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decodeCode |= * inData ++; \
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decodeRange <<= 8; \
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decodeLow <<= 8; \
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} \
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}
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#define ENET_CONTEXT_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, createRoot, visitNode, createRight, createLeft) \
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{ \
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under_ = 0; \
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count_ = minimum; \
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if (! (context) -> symbols) \
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{ \
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createRoot; \
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} \
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else \
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{ \
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ENetSymbol * node = (context) + (context) -> symbols; \
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for (;;) \
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{ \
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enet_uint16 after = under_ + node -> under + (node -> value + 1)*minimum, before = node -> count + minimum; \
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visitNode; \
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if (code >= after) \
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{ \
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under_ += node -> under; \
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if (node -> right) { node += node -> right; continue; } \
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createRight; \
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} \
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else \
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if (code < after - before) \
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{ \
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node -> under += update; \
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if (node -> left) { node += node -> left; continue; } \
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createLeft; \
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} \
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else \
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{ \
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value_ = node -> value; \
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count_ += node -> count; \
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under_ = after - before; \
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node -> under += update; \
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node -> count += update; \
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symbol_ = node; \
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} \
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break; \
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} \
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} \
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}
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#define ENET_CONTEXT_TRY_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, exclude) \
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ENET_CONTEXT_DECODE (context, symbol_, code, value_, under_, count_, update, minimum, return 0, exclude (node -> value, after, before), return 0, return 0)
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#define ENET_CONTEXT_ROOT_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, exclude) \
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ENET_CONTEXT_DECODE (context, symbol_, code, value_, under_, count_, update, minimum, \
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{ \
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value_ = code / minimum; \
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under_ = code - code%minimum; \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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(context) -> symbols = symbol_ - (context); \
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}, \
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exclude (node -> value, after, before), \
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{ \
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value_ = node->value + 1 + (code - after)/minimum; \
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under_ = code - (code - after)%minimum; \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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node -> right = symbol_ - node; \
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}, \
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{ \
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value_ = node->value - 1 - (after - before - code - 1)/minimum; \
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under_ = code - (after - before - code - 1)%minimum; \
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ENET_SYMBOL_CREATE (symbol_, value_, update); \
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node -> left = symbol_ - node; \
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}) \
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#ifdef ENET_CONTEXT_EXCLUSION
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typedef struct _ENetExclude
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{
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enet_uint8 value;
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enet_uint16 under;
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} ENetExclude;
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#define ENET_CONTEXT_DECODE_EXCLUDE(context, total, minimum) \
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{ \
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enet_uint16 under = 0; \
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nextExclude = excludes; \
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ENET_CONTEXT_WALK (context, { \
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under += rangeCoder -> symbols [node -> parent].count + minimum; \
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nextExclude -> value = node -> value; \
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nextExclude -> under = under; \
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nextExclude ++; \
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}); \
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total -= under; \
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}
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#define ENET_CONTEXT_EXCLUDED(value_, after, before) \
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{ \
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size_t low = 0, high = nextExclude - excludes; \
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for(;;) \
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{ \
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size_t mid = (low + high) >> 1; \
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const ENetExclude * exclude = & excludes [mid]; \
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if (value_ < exclude -> value) \
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{ \
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if (low + 1 < high) \
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{ \
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high = mid; \
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continue; \
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} \
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if (exclude > excludes) \
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after -= exclude [-1].under; \
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} \
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else \
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{ \
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if (value_ > exclude -> value) \
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{ \
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if (low + 1 < high) \
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{ \
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low = mid; \
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continue; \
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} \
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} \
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else \
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before = 0; \
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after -= exclude -> under; \
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} \
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break; \
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} \
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}
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#endif
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#define ENET_CONTEXT_NOT_EXCLUDED(value_, after, before)
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size_t
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enet_range_coder_decompress (void * context, const enet_uint8 * inData, size_t inLimit, enet_uint8 * outData, size_t outLimit)
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{
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ENetRangeCoder * rangeCoder = (ENetRangeCoder *) context;
|
|
enet_uint8 * outStart = outData, * outEnd = & outData [outLimit];
|
|
const enet_uint8 * inEnd = & inData [inLimit];
|
|
enet_uint32 decodeLow = 0, decodeCode = 0, decodeRange = ~0;
|
|
ENetSymbol * root;
|
|
enet_uint16 predicted = 0;
|
|
size_t order = 0, nextSymbol = 0;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
ENetExclude excludes [256];
|
|
ENetExclude * nextExclude = excludes;
|
|
#endif
|
|
|
|
if (rangeCoder == NULL || inLimit <= 0)
|
|
return 0;
|
|
|
|
ENET_CONTEXT_CREATE (root, ENET_CONTEXT_ESCAPE_MINIMUM, ENET_CONTEXT_SYMBOL_MINIMUM);
|
|
|
|
ENET_RANGE_CODER_SEED;
|
|
|
|
for (;;)
|
|
{
|
|
ENetSymbol * subcontext, * symbol, * patch;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
const ENetSymbol * childContext = & emptyContext;
|
|
#endif
|
|
enet_uint8 value = 0;
|
|
enet_uint16 code, under, count, bottom, * parent = & predicted, total;
|
|
|
|
for (subcontext = & rangeCoder -> symbols [predicted];
|
|
subcontext != root;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
childContext = subcontext,
|
|
#endif
|
|
subcontext = & rangeCoder -> symbols [subcontext -> parent])
|
|
{
|
|
if (subcontext -> escapes <= 0)
|
|
continue;
|
|
total = subcontext -> total;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
if (childContext -> total > 0)
|
|
ENET_CONTEXT_DECODE_EXCLUDE (childContext, total, 0);
|
|
#endif
|
|
if (subcontext -> escapes >= total)
|
|
continue;
|
|
code = ENET_RANGE_CODER_READ (total);
|
|
if (code < subcontext -> escapes)
|
|
{
|
|
ENET_RANGE_CODER_DECODE (0, subcontext -> escapes, total);
|
|
continue;
|
|
}
|
|
code -= subcontext -> escapes;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
if (childContext -> total > 0)
|
|
{
|
|
ENET_CONTEXT_TRY_DECODE (subcontext, symbol, code, value, under, count, ENET_SUBCONTEXT_SYMBOL_DELTA, 0, ENET_CONTEXT_EXCLUDED);
|
|
}
|
|
else
|
|
#endif
|
|
{
|
|
ENET_CONTEXT_TRY_DECODE (subcontext, symbol, code, value, under, count, ENET_SUBCONTEXT_SYMBOL_DELTA, 0, ENET_CONTEXT_NOT_EXCLUDED);
|
|
}
|
|
bottom = symbol - rangeCoder -> symbols;
|
|
ENET_RANGE_CODER_DECODE (subcontext -> escapes + under, count, total);
|
|
subcontext -> total += ENET_SUBCONTEXT_SYMBOL_DELTA;
|
|
if (count > 0xFF - 2*ENET_SUBCONTEXT_SYMBOL_DELTA || subcontext -> total > ENET_RANGE_CODER_BOTTOM - 0x100)
|
|
ENET_CONTEXT_RESCALE (subcontext, 0);
|
|
goto patchContexts;
|
|
}
|
|
|
|
total = root -> total;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
if (childContext -> total > 0)
|
|
ENET_CONTEXT_DECODE_EXCLUDE (childContext, total, ENET_CONTEXT_SYMBOL_MINIMUM);
|
|
#endif
|
|
code = ENET_RANGE_CODER_READ (total);
|
|
if (code < root -> escapes)
|
|
{
|
|
ENET_RANGE_CODER_DECODE (0, root -> escapes, total);
|
|
break;
|
|
}
|
|
code -= root -> escapes;
|
|
#ifdef ENET_CONTEXT_EXCLUSION
|
|
if (childContext -> total > 0)
|
|
{
|
|
ENET_CONTEXT_ROOT_DECODE (root, symbol, code, value, under, count, ENET_CONTEXT_SYMBOL_DELTA, ENET_CONTEXT_SYMBOL_MINIMUM, ENET_CONTEXT_EXCLUDED);
|
|
}
|
|
else
|
|
#endif
|
|
{
|
|
ENET_CONTEXT_ROOT_DECODE (root, symbol, code, value, under, count, ENET_CONTEXT_SYMBOL_DELTA, ENET_CONTEXT_SYMBOL_MINIMUM, ENET_CONTEXT_NOT_EXCLUDED);
|
|
}
|
|
bottom = symbol - rangeCoder -> symbols;
|
|
ENET_RANGE_CODER_DECODE (root -> escapes + under, count, total);
|
|
root -> total += ENET_CONTEXT_SYMBOL_DELTA;
|
|
if (count > 0xFF - 2*ENET_CONTEXT_SYMBOL_DELTA + ENET_CONTEXT_SYMBOL_MINIMUM || root -> total > ENET_RANGE_CODER_BOTTOM - 0x100)
|
|
ENET_CONTEXT_RESCALE (root, ENET_CONTEXT_SYMBOL_MINIMUM);
|
|
|
|
patchContexts:
|
|
for (patch = & rangeCoder -> symbols [predicted];
|
|
patch != subcontext;
|
|
patch = & rangeCoder -> symbols [patch -> parent])
|
|
{
|
|
ENET_CONTEXT_ENCODE (patch, symbol, value, under, count, ENET_SUBCONTEXT_SYMBOL_DELTA, 0);
|
|
* parent = symbol - rangeCoder -> symbols;
|
|
parent = & symbol -> parent;
|
|
if (count <= 0)
|
|
{
|
|
patch -> escapes += ENET_SUBCONTEXT_ESCAPE_DELTA;
|
|
patch -> total += ENET_SUBCONTEXT_ESCAPE_DELTA;
|
|
}
|
|
patch -> total += ENET_SUBCONTEXT_SYMBOL_DELTA;
|
|
if (count > 0xFF - 2*ENET_SUBCONTEXT_SYMBOL_DELTA || patch -> total > ENET_RANGE_CODER_BOTTOM - 0x100)
|
|
ENET_CONTEXT_RESCALE (patch, 0);
|
|
}
|
|
* parent = bottom;
|
|
|
|
ENET_RANGE_CODER_OUTPUT (value);
|
|
|
|
if (order >= ENET_SUBCONTEXT_ORDER)
|
|
predicted = rangeCoder -> symbols [predicted].parent;
|
|
else
|
|
order ++;
|
|
ENET_RANGE_CODER_FREE_SYMBOLS;
|
|
}
|
|
|
|
return (size_t) (outData - outStart);
|
|
}
|
|
|
|
/** @defgroup host ENet host functions
|
|
@{
|
|
*/
|
|
|
|
/** Sets the packet compressor the host should use to the default range coder.
|
|
@param host host to enable the range coder for
|
|
@returns 0 on success, < 0 on failure
|
|
*/
|
|
int
|
|
enet_host_compress_with_range_coder (ENetHost * host)
|
|
{
|
|
ENetCompressor compressor;
|
|
memset (& compressor, 0, sizeof (compressor));
|
|
compressor.context = enet_range_coder_create();
|
|
if (compressor.context == NULL)
|
|
return -1;
|
|
compressor.compress = enet_range_coder_compress;
|
|
compressor.decompress = enet_range_coder_decompress;
|
|
compressor.destroy = enet_range_coder_destroy;
|
|
enet_host_compress (host, & compressor);
|
|
return 0;
|
|
}
|
|
|
|
/** @} */
|
|
|
|
|