added missing compress.c

compress.c

@@ -0,0 +1,649 @@
+/** 
+ @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);
+}
+
+/** 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;
+}
+    
+    
+