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authorAndrei Karas <akaras@inbox.ru>2011-01-02 01:48:38 +0200
committerAndrei Karas <akaras@inbox.ru>2011-01-02 02:41:24 +0200
commit3eeae12c498d1a4dbe969462d2ba841f77ee3ccb (patch)
treeff8eab35e732bc0749fc11677c8873a7b3a58704 /src/enet/compress.c
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Initial commit.
This code based on mana client http://www.gitorious.org/mana/mana and my private repository.
Diffstat (limited to 'src/enet/compress.c')
-rw-r--r--src/enet/compress.c654
1 files changed, 654 insertions, 0 deletions
diff --git a/src/enet/compress.c b/src/enet/compress.c
new file mode 100644
index 000000000..784489a78
--- /dev/null
+++ b/src/enet/compress.c
@@ -0,0 +1,654 @@
+/**
+ @file compress.c
+ @brief An adaptive order-2 PPM range coder
+*/
+#define ENET_BUILDING_LIB 1
+#include <string.h>
+#include "enet/enet.h"
+
+typedef struct _ENetSymbol
+{
+ /* binary indexed tree of symbols */
+ enet_uint8 value;
+ enet_uint8 count;
+ enet_uint16 under;
+ enet_uint16 left, right;
+
+ /* context defined by this symbol */
+ enet_uint16 symbols;
+ enet_uint16 escapes;
+ enet_uint16 total;
+ enet_uint16 parent;
+} ENetSymbol;
+
+/* adaptation constants tuned aggressively for small packet sizes rather than large file compression */
+enum
+{
+ ENET_RANGE_CODER_TOP = 1<<24,
+ ENET_RANGE_CODER_BOTTOM = 1<<16,
+
+ ENET_CONTEXT_SYMBOL_DELTA = 3,
+ ENET_CONTEXT_SYMBOL_MINIMUM = 1,
+ ENET_CONTEXT_ESCAPE_MINIMUM = 1,
+
+ ENET_SUBCONTEXT_ORDER = 2,
+ ENET_SUBCONTEXT_SYMBOL_DELTA = 2,
+ ENET_SUBCONTEXT_ESCAPE_DELTA = 5
+};
+
+/* context exclusion roughly halves compression speed, so disable for now */
+#undef ENET_CONTEXT_EXCLUSION
+
+typedef struct _ENetRangeCoder
+{
+ /* only allocate enough symbols for reasonable MTUs, would need to be larger for large file compression */
+ ENetSymbol symbols[4096];
+} ENetRangeCoder;
+
+void *
+enet_range_coder_create (void)
+{
+ ENetRangeCoder * rangeCoder = (ENetRangeCoder *) enet_malloc (sizeof (ENetRangeCoder));
+ if (rangeCoder == NULL)
+ return NULL;
+
+ return rangeCoder;
+}
+
+void
+enet_range_coder_destroy (void * context)
+{
+ ENetRangeCoder * rangeCoder = (ENetRangeCoder *) context;
+ if (rangeCoder == NULL)
+ return;
+
+ enet_free (rangeCoder);
+}
+
+#define ENET_SYMBOL_CREATE(symbol, value_, count_) \
+{ \
+ symbol = & rangeCoder -> symbols [nextSymbol ++]; \
+ symbol -> value = value_; \
+ symbol -> count = count_; \
+ symbol -> under = count_; \
+ symbol -> left = 0; \
+ symbol -> right = 0; \
+ symbol -> symbols = 0; \
+ symbol -> escapes = 0; \
+ symbol -> total = 0; \
+ symbol -> parent = 0; \
+}
+
+#define ENET_CONTEXT_CREATE(context, escapes_, minimum) \
+{ \
+ ENET_SYMBOL_CREATE (context, 0, 0); \
+ (context) -> escapes = escapes_; \
+ (context) -> total = escapes_ + 256*minimum; \
+ (context) -> symbols = 0; \
+}
+
+static enet_uint16
+enet_symbol_rescale (ENetSymbol * symbol)
+{
+ enet_uint16 total = 0;
+ for (;;)
+ {
+ symbol -> count -= symbol->count >> 1;
+ symbol -> under = symbol -> count;
+ if (symbol -> left)
+ symbol -> under += enet_symbol_rescale (symbol + symbol -> left);
+ total += symbol -> under;
+ if (! symbol -> right) break;
+ symbol += symbol -> right;
+ }
+ return total;
+}
+
+#define ENET_CONTEXT_RESCALE(context, minimum) \
+{ \
+ (context) -> total = (context) -> symbols ? enet_symbol_rescale ((context) + (context) -> symbols) : 0; \
+ (context) -> escapes -= (context) -> escapes >> 1; \
+ (context) -> total += (context) -> escapes + 256*minimum; \
+}
+
+#define ENET_RANGE_CODER_OUTPUT(value) \
+{ \
+ if (outData >= outEnd) \
+ return 0; \
+ * outData ++ = value; \
+}
+
+#define ENET_RANGE_CODER_ENCODE(under, count, total) \
+{ \
+ encodeRange /= (total); \
+ encodeLow += (under) * encodeRange; \
+ encodeRange *= (count); \
+ for (;;) \
+ { \
+ if((encodeLow ^ (encodeLow + encodeRange)) >= ENET_RANGE_CODER_TOP) \
+ { \
+ if(encodeRange >= ENET_RANGE_CODER_BOTTOM) break; \
+ encodeRange = -encodeLow & (ENET_RANGE_CODER_BOTTOM - 1); \
+ } \
+ ENET_RANGE_CODER_OUTPUT (encodeLow >> 24); \
+ encodeRange <<= 8; \
+ encodeLow <<= 8; \
+ } \
+}
+
+#define ENET_RANGE_CODER_FLUSH \
+{ \
+ while (encodeLow) \
+ { \
+ ENET_RANGE_CODER_OUTPUT (encodeLow >> 24); \
+ encodeLow <<= 8; \
+ } \
+}
+
+#define ENET_RANGE_CODER_FREE_SYMBOLS \
+{ \
+ if (nextSymbol >= sizeof (rangeCoder -> symbols) / sizeof (ENetSymbol) - ENET_SUBCONTEXT_ORDER ) \
+ { \
+ nextSymbol = 0; \
+ ENET_CONTEXT_CREATE (root, ENET_CONTEXT_ESCAPE_MINIMUM, ENET_CONTEXT_SYMBOL_MINIMUM); \
+ predicted = 0; \
+ order = 0; \
+ } \
+}
+
+#define ENET_CONTEXT_ENCODE(context, symbol_, value_, under_, count_, update, minimum) \
+{ \
+ under_ = value*minimum; \
+ count_ = minimum; \
+ if (! (context) -> symbols) \
+ { \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ (context) -> symbols = symbol_ - (context); \
+ } \
+ else \
+ { \
+ ENetSymbol * node = (context) + (context) -> symbols; \
+ for (;;) \
+ { \
+ if (value_ < node -> value) \
+ { \
+ node -> under += update; \
+ if (node -> left) { node += node -> left; continue; } \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ node -> left = symbol_ - node; \
+ } \
+ else \
+ if (value_ > node -> value) \
+ { \
+ under_ += node -> under; \
+ if (node -> right) { node += node -> right; continue; } \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ node -> right = symbol_ - node; \
+ } \
+ else \
+ { \
+ count_ += node -> count; \
+ under_ += node -> under - node -> count; \
+ node -> under += update; \
+ node -> count += update; \
+ symbol_ = node; \
+ } \
+ break; \
+ } \
+ } \
+}
+
+#ifdef ENET_CONTEXT_EXCLUSION
+static const ENetSymbol emptyContext = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+
+#define ENET_CONTEXT_WALK(context, body) \
+{ \
+ const ENetSymbol * node = (context) + (context) -> symbols; \
+ const ENetSymbol * stack [256]; \
+ size_t stackSize = 0; \
+ while (node -> left) \
+ { \
+ stack [stackSize ++] = node; \
+ node += node -> left; \
+ } \
+ for (;;) \
+ { \
+ body; \
+ if (node -> right) \
+ { \
+ node += node -> right; \
+ while (node -> left) \
+ { \
+ stack [stackSize ++] = node; \
+ node += node -> left; \
+ } \
+ } \
+ else \
+ if (stackSize <= 0) \
+ break; \
+ else \
+ node = stack [-- stackSize]; \
+ } \
+}
+
+#define ENET_CONTEXT_ENCODE_EXCLUDE(context, value_, under, total, minimum) \
+ENET_CONTEXT_WALK(context, { \
+ if (node -> value != value_) \
+ { \
+ enet_uint16 parentCount = rangeCoder -> symbols [node -> parent].count + minimum; \
+ if (node -> value < value_) \
+ under -= parentCount; \
+ total -= parentCount; \
+ } \
+})
+#endif
+
+size_t
+enet_range_coder_compress (void * context, const ENetBuffer * inBuffers, size_t inBufferCount, size_t inLimit, enet_uint8 * outData, size_t outLimit)
+{
+ ENetRangeCoder * rangeCoder = (ENetRangeCoder *) context;
+ enet_uint8 * outStart = outData, * outEnd = & outData [outLimit];
+ const enet_uint8 * inData, * inEnd;
+ enet_uint32 encodeLow = 0, encodeRange = ~0;
+ ENetSymbol * root;
+ enet_uint16 predicted = 0;
+ size_t order = 0, nextSymbol = 0;
+
+ if (rangeCoder == NULL || inBufferCount <= 0 || inLimit <= 0)
+ return 0;
+
+ inData = (const enet_uint8 *) inBuffers -> data;
+ inEnd = & inData [inBuffers -> dataLength];
+ inBuffers ++;
+ inBufferCount --;
+
+ ENET_CONTEXT_CREATE (root, ENET_CONTEXT_ESCAPE_MINIMUM, ENET_CONTEXT_SYMBOL_MINIMUM);
+
+ for (;;)
+ {
+ ENetSymbol * subcontext, * symbol;
+#ifdef ENET_CONTEXT_EXCLUSION
+ const ENetSymbol * childContext = & emptyContext;
+#endif
+ enet_uint8 value;
+ enet_uint16 count, under, * parent = & predicted, total;
+ if (inData >= inEnd)
+ {
+ if (inBufferCount <= 0)
+ break;
+ inData = (const enet_uint8 *) inBuffers -> data;
+ inEnd = & inData [inBuffers -> dataLength];
+ inBuffers ++;
+ inBufferCount --;
+ }
+ value = * inData ++;
+
+ for (subcontext = & rangeCoder -> symbols [predicted];
+ subcontext != root;
+#ifdef ENET_CONTEXT_EXCLUSION
+ childContext = subcontext,
+#endif
+ subcontext = & rangeCoder -> symbols [subcontext -> parent])
+ {
+ ENET_CONTEXT_ENCODE (subcontext, symbol, value, under, count, ENET_SUBCONTEXT_SYMBOL_DELTA, 0);
+ * parent = symbol - rangeCoder -> symbols;
+ parent = & symbol -> parent;
+ total = subcontext -> total;
+#ifdef ENET_CONTEXT_EXCLUSION
+ if (childContext -> total > ENET_SUBCONTEXT_SYMBOL_DELTA + ENET_SUBCONTEXT_ESCAPE_DELTA)
+ ENET_CONTEXT_ENCODE_EXCLUDE (childContext, value, under, total, 0);
+#endif
+ if (count > 0)
+ {
+ ENET_RANGE_CODER_ENCODE (subcontext -> escapes + under, count, total);
+ }
+ else
+ {
+ if (subcontext -> escapes > 0 && subcontext -> escapes < total)
+ ENET_RANGE_CODER_ENCODE (0, subcontext -> escapes, total);
+ subcontext -> escapes += ENET_SUBCONTEXT_ESCAPE_DELTA;
+ subcontext -> total += ENET_SUBCONTEXT_ESCAPE_DELTA;
+ }
+ 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);
+ if (count > 0) goto nextInput;
+ }
+
+ ENET_CONTEXT_ENCODE (root, symbol, value, under, count, ENET_CONTEXT_SYMBOL_DELTA, ENET_CONTEXT_SYMBOL_MINIMUM);
+ * parent = symbol - rangeCoder -> symbols;
+ parent = & symbol -> parent;
+ total = root -> total;
+#ifdef ENET_CONTEXT_EXCLUSION
+ if (childContext -> total > ENET_SUBCONTEXT_SYMBOL_DELTA + ENET_SUBCONTEXT_ESCAPE_DELTA)
+ ENET_CONTEXT_ENCODE_EXCLUDE (childContext, value, under, total, ENET_CONTEXT_SYMBOL_MINIMUM);
+#endif
+ ENET_RANGE_CODER_ENCODE (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);
+
+ nextInput:
+ if (order >= ENET_SUBCONTEXT_ORDER)
+ predicted = rangeCoder -> symbols [predicted].parent;
+ else
+ order ++;
+ ENET_RANGE_CODER_FREE_SYMBOLS;
+ }
+
+ ENET_RANGE_CODER_FLUSH;
+
+ return (size_t) (outData - outStart);
+}
+
+#define ENET_RANGE_CODER_SEED \
+{ \
+ if (inData < inEnd) decodeCode |= * inData ++ << 24; \
+ if (inData < inEnd) decodeCode |= * inData ++ << 16; \
+ if (inData < inEnd) decodeCode |= * inData ++ << 8; \
+ if (inData < inEnd) decodeCode |= * inData ++; \
+}
+
+#define ENET_RANGE_CODER_READ(total) ((decodeCode - decodeLow) / (decodeRange /= (total)))
+
+#define ENET_RANGE_CODER_DECODE(under, count, total) \
+{ \
+ decodeLow += (under) * decodeRange; \
+ decodeRange *= (count); \
+ for (;;) \
+ { \
+ if((decodeLow ^ (decodeLow + decodeRange)) >= ENET_RANGE_CODER_TOP) \
+ { \
+ if(decodeRange >= ENET_RANGE_CODER_BOTTOM) break; \
+ decodeRange = -decodeLow & (ENET_RANGE_CODER_BOTTOM - 1); \
+ } \
+ decodeCode <<= 8; \
+ if (inData < inEnd) \
+ decodeCode |= * inData ++; \
+ decodeRange <<= 8; \
+ decodeLow <<= 8; \
+ } \
+}
+
+#define ENET_CONTEXT_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, createRoot, visitNode, createRight, createLeft) \
+{ \
+ under_ = 0; \
+ count_ = minimum; \
+ if (! (context) -> symbols) \
+ { \
+ createRoot; \
+ } \
+ else \
+ { \
+ ENetSymbol * node = (context) + (context) -> symbols; \
+ for (;;) \
+ { \
+ enet_uint16 after = under_ + node -> under + (node -> value + 1)*minimum, before = node -> count + minimum; \
+ visitNode; \
+ if (code >= after) \
+ { \
+ under_ += node -> under; \
+ if (node -> right) { node += node -> right; continue; } \
+ createRight; \
+ } \
+ else \
+ if (code < after - before) \
+ { \
+ node -> under += update; \
+ if (node -> left) { node += node -> left; continue; } \
+ createLeft; \
+ } \
+ else \
+ { \
+ value_ = node -> value; \
+ count_ += node -> count; \
+ under_ = after - before; \
+ node -> under += update; \
+ node -> count += update; \
+ symbol_ = node; \
+ } \
+ break; \
+ } \
+ } \
+}
+
+#define ENET_CONTEXT_TRY_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, exclude) \
+ENET_CONTEXT_DECODE (context, symbol_, code, value_, under_, count_, update, minimum, return 0, exclude (node -> value, after, before), return 0, return 0)
+
+#define ENET_CONTEXT_ROOT_DECODE(context, symbol_, code, value_, under_, count_, update, minimum, exclude) \
+ENET_CONTEXT_DECODE (context, symbol_, code, value_, under_, count_, update, minimum, \
+ { \
+ value_ = code / minimum; \
+ under_ = code - code%minimum; \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ (context) -> symbols = symbol_ - (context); \
+ }, \
+ exclude (node -> value, after, before), \
+ { \
+ value_ = node->value + 1 + (code - after)/minimum; \
+ under_ = code - (code - after)%minimum; \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ node -> right = symbol_ - node; \
+ }, \
+ { \
+ value_ = node->value - 1 - (after - before - code - 1)/minimum; \
+ under_ = code - (after - before - code - 1)%minimum; \
+ ENET_SYMBOL_CREATE (symbol_, value_, update); \
+ node -> left = symbol_ - node; \
+ }) \
+
+#ifdef ENET_CONTEXT_EXCLUSION
+typedef struct _ENetExclude
+{
+ enet_uint8 value;
+ enet_uint16 under;
+} ENetExclude;
+
+#define ENET_CONTEXT_DECODE_EXCLUDE(context, total, minimum) \
+{ \
+ enet_uint16 under = 0; \
+ nextExclude = excludes; \
+ ENET_CONTEXT_WALK (context, { \
+ under += rangeCoder -> symbols [node -> parent].count + minimum; \
+ nextExclude -> value = node -> value; \
+ nextExclude -> under = under; \
+ nextExclude ++; \
+ }); \
+ total -= under; \
+}
+
+#define ENET_CONTEXT_EXCLUDED(value_, after, before) \
+{ \
+ size_t low = 0, high = nextExclude - excludes; \
+ for(;;) \
+ { \
+ size_t mid = (low + high) >> 1; \
+ const ENetExclude * exclude = & excludes [mid]; \
+ if (value_ < exclude -> value) \
+ { \
+ if (low + 1 < high) \
+ { \
+ high = mid; \
+ continue; \
+ } \
+ if (exclude > excludes) \
+ after -= exclude [-1].under; \
+ } \
+ else \
+ { \
+ if (value_ > exclude -> value) \
+ { \
+ if (low + 1 < high) \
+ { \
+ low = mid; \
+ continue; \
+ } \
+ } \
+ else \
+ before = 0; \
+ after -= exclude -> under; \
+ } \
+ break; \
+ } \
+}
+#endif
+
+#define ENET_CONTEXT_NOT_EXCLUDED(value_, after, before)
+
+size_t
+enet_range_coder_decompress (void * context, const enet_uint8 * inData, size_t inLimit, enet_uint8 * outData, size_t outLimit)
+{
+ 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;
+}
+
+/** @} */
+
+