Merge pull request #515 from svpv/refactorDec

lz4.c: refactor the decoding routines

1 files changed, 114 insertions, 49 deletions

diff --git a/lib/lz4.c b/lib/lz4.c
index 06ff611..1e0d8e9 100644
--- a/lib/lz4.c
+++ b/lib/lz4.c
@@ -92,6 +92,7 @@
 *  Dependency
 **************************************/
 #define LZ4_STATIC_LINKING_ONLY
+#define LZ4_DISABLE_DEPRECATE_WARNINGS /* due to LZ4_decompress_safe_withPrefix64k */
 #include "lz4.h"
 /* see also "memory routines" below */
 
@@ -1554,6 +1555,8 @@ _output_error:
 }
 
 
+/*===== Instantiate the API decoding functions. =====*/
+
 LZ4_FORCE_O2_GCC_PPC64LE
 int LZ4_decompress_safe(const char* source, char* dest, int compressedSize, int maxDecompressedSize)
 {
@@ -1575,9 +1578,76 @@ int LZ4_decompress_fast(const char* source, char* dest, int originalSize)
 {
     return LZ4_decompress_generic(source, dest, 0, originalSize,
                                   endOnOutputSize, full, 0, withPrefix64k,
-                                  (BYTE*)(dest - 64 KB), NULL, 64 KB);
+                                  (BYTE*)dest - 64 KB, NULL, 0);
+}
+
+/*===== Instantiate a few more decoding cases, used more than once. =====*/
+
+LZ4_FORCE_O2_GCC_PPC64LE /* Exported, an obsolete API function. */
+int LZ4_decompress_safe_withPrefix64k(const char* source, char* dest, int compressedSize, int maxOutputSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  endOnInputSize, full, 0, withPrefix64k,
+                                  (BYTE*)dest - 64 KB, NULL, 0);
+}
+
+/* Another obsolete API function, paired with the previous one. */
+int LZ4_decompress_fast_withPrefix64k(const char* source, char* dest, int originalSize)
+{
+    /* LZ4_decompress_fast doesn't validate match offsets,
+     * and thus serves well with any prefixed dictionary. */
+    return LZ4_decompress_fast(source, dest, originalSize);
+}
+
+LZ4_FORCE_O2_GCC_PPC64LE
+static int LZ4_decompress_safe_withSmallPrefix(const char* source, char* dest, int compressedSize, int maxOutputSize,
+                                               size_t prefixSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  endOnInputSize, full, 0, noDict,
+                                  (BYTE*)dest-prefixSize, NULL, 0);
 }
 
+LZ4_FORCE_O2_GCC_PPC64LE /* Exported under another name, for tests/fullbench.c */
+#define LZ4_decompress_safe_extDict LZ4_decompress_safe_forceExtDict
+int LZ4_decompress_safe_extDict(const char* source, char* dest, int compressedSize, int maxOutputSize,
+                                const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  endOnInputSize, full, 0, usingExtDict,
+                                  (BYTE*)dest, (const BYTE*)dictStart, dictSize);
+}
+
+LZ4_FORCE_O2_GCC_PPC64LE
+static int LZ4_decompress_fast_extDict(const char* source, char* dest, int originalSize,
+                                       const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_generic(source, dest, 0, originalSize,
+                                  endOnOutputSize, full, 0, usingExtDict,
+                                  (BYTE*)dest, (const BYTE*)dictStart, dictSize);
+}
+
+/* The "double dictionary" mode, for use with e.g. ring buffers: the first part
+ * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
+ * These routines are used only once, in LZ4_decompress_*_continue().
+ */
+LZ4_FORCE_INLINE
+int LZ4_decompress_safe_doubleDict(const char* source, char* dest, int compressedSize, int maxOutputSize,
+                                   size_t prefixSize, const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
+                                  endOnInputSize, full, 0, usingExtDict,
+                                  (BYTE*)dest-prefixSize, (const BYTE*)dictStart, dictSize);
+}
+
+LZ4_FORCE_INLINE
+int LZ4_decompress_fast_doubleDict(const char* source, char* dest, int originalSize,
+                                   size_t prefixSize, const void* dictStart, size_t dictSize)
+{
+    return LZ4_decompress_generic(source, dest, 0, originalSize,
+                                  endOnOutputSize, full, 0, usingExtDict,
+                                  (BYTE*)dest-prefixSize, (const BYTE*)dictStart, dictSize);
+}
 
 /*===== streaming decompression functions =====*/
 
@@ -1624,19 +1694,32 @@ int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const ch
     LZ4_streamDecode_t_internal* lz4sd = &LZ4_streamDecode->internal_donotuse;
     int result;
 
-    if (lz4sd->prefixEnd == (BYTE*)dest) {
-        result = LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
-                                        endOnInputSize, full, 0,
-                                        usingExtDict, lz4sd->prefixEnd - lz4sd->prefixSize, lz4sd->externalDict, lz4sd->extDictSize);
+    if (lz4sd->prefixSize == 0) {
+        /* The first call, no dictionary yet. */
+        assert(lz4sd->extDictSize == 0);
+        result = LZ4_decompress_safe(source, dest, compressedSize, maxOutputSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = result;
+        lz4sd->prefixEnd = (BYTE*)dest + result;
+    } else if (lz4sd->prefixEnd == (BYTE*)dest) {
+        /* They're rolling the current segment. */
+        if (lz4sd->prefixSize >= 64 KB - 1)
+            result = LZ4_decompress_safe_withPrefix64k(source, dest, compressedSize, maxOutputSize);
+        else if (lz4sd->extDictSize == 0)
+            result = LZ4_decompress_safe_withSmallPrefix(source, dest, compressedSize, maxOutputSize,
+                                                         lz4sd->prefixSize);
+        else
+            result = LZ4_decompress_safe_doubleDict(source, dest, compressedSize, maxOutputSize,
+                                                    lz4sd->prefixSize, lz4sd->externalDict, lz4sd->extDictSize);
         if (result <= 0) return result;
         lz4sd->prefixSize += result;
         lz4sd->prefixEnd  += result;
     } else {
+        /* The buffer wraps around, or they're switching to another buffer. */
         lz4sd->extDictSize = lz4sd->prefixSize;
         lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
-        result = LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize,
-                                        endOnInputSize, full, 0,
-                                        usingExtDict, (BYTE*)dest, lz4sd->externalDict, lz4sd->extDictSize);
+        result = LZ4_decompress_safe_extDict(source, dest, compressedSize, maxOutputSize,
+                                             lz4sd->externalDict, lz4sd->extDictSize);
         if (result <= 0) return result;
         lz4sd->prefixSize = result;
         lz4sd->prefixEnd  = (BYTE*)dest + result;
@@ -1651,19 +1734,26 @@ int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const ch
     LZ4_streamDecode_t_internal* lz4sd = &LZ4_streamDecode->internal_donotuse;
     int result;
 
-    if (lz4sd->prefixEnd == (BYTE*)dest) {
-        result = LZ4_decompress_generic(source, dest, 0, originalSize,
-                                        endOnOutputSize, full, 0,
-                                        usingExtDict, lz4sd->prefixEnd - lz4sd->prefixSize, lz4sd->externalDict, lz4sd->extDictSize);
+    if (lz4sd->prefixSize == 0) {
+        assert(lz4sd->extDictSize == 0);
+        result = LZ4_decompress_fast(source, dest, originalSize);
+        if (result <= 0) return result;
+        lz4sd->prefixSize = originalSize;
+        lz4sd->prefixEnd = (BYTE*)dest + originalSize;
+    } else if (lz4sd->prefixEnd == (BYTE*)dest) {
+        if (lz4sd->prefixSize >= 64 KB - 1 || lz4sd->extDictSize == 0)
+            result = LZ4_decompress_fast(source, dest, originalSize);
+        else
+            result = LZ4_decompress_fast_doubleDict(source, dest, originalSize,
+                                                    lz4sd->prefixSize, lz4sd->externalDict, lz4sd->extDictSize);
         if (result <= 0) return result;
         lz4sd->prefixSize += originalSize;
         lz4sd->prefixEnd  += originalSize;
     } else {
         lz4sd->extDictSize = lz4sd->prefixSize;
         lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
-        result = LZ4_decompress_generic(source, dest, 0, originalSize,
-                                        endOnOutputSize, full, 0,
-                                        usingExtDict, (BYTE*)dest, lz4sd->externalDict, lz4sd->extDictSize);
+        result = LZ4_decompress_fast_extDict(source, dest, originalSize,
+                                             lz4sd->externalDict, lz4sd->extDictSize);
         if (result <= 0) return result;
         lz4sd->prefixSize = originalSize;
         lz4sd->prefixEnd  = (BYTE*)dest + originalSize;
@@ -1680,36 +1770,23 @@ Advanced decoding functions :
     the dictionary must be explicitly provided within parameters
 */
 
-LZ4_FORCE_O2_GCC_PPC64LE
-LZ4_FORCE_INLINE int LZ4_decompress_usingDict_generic(const char* source, char* dest, int compressedSize, int maxOutputSize, int safe, const char* dictStart, int dictSize)
+int LZ4_decompress_safe_usingDict(const char* source, char* dest, int compressedSize, int maxOutputSize, const char* dictStart, int dictSize)
 {
     if (dictSize==0)
-        return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, safe, full, 0, noDict, (BYTE*)dest, NULL, 0);
+        return LZ4_decompress_safe(source, dest, compressedSize, maxOutputSize);
     if (dictStart+dictSize == dest) {
-        if (dictSize >= (int)(64 KB - 1))
-            return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, safe, full, 0, withPrefix64k, (BYTE*)dest-64 KB, NULL, 0);
-        return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, safe, full, 0, noDict, (BYTE*)dest-dictSize, NULL, 0);
+        if (dictSize >= 64 KB - 1)
+            return LZ4_decompress_safe_withPrefix64k(source, dest, compressedSize, maxOutputSize);
+        return LZ4_decompress_safe_withSmallPrefix(source, dest, compressedSize, maxOutputSize, dictSize);
     }
-    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, safe, full, 0, usingExtDict, (BYTE*)dest, (const BYTE*)dictStart, dictSize);
-}
-
-LZ4_FORCE_O2_GCC_PPC64LE
-int LZ4_decompress_safe_usingDict(const char* source, char* dest, int compressedSize, int maxOutputSize, const char* dictStart, int dictSize)
-{
-    return LZ4_decompress_usingDict_generic(source, dest, compressedSize, maxOutputSize, 1, dictStart, dictSize);
+    return LZ4_decompress_safe_extDict(source, dest, compressedSize, maxOutputSize, dictStart, dictSize);
 }
 
-LZ4_FORCE_O2_GCC_PPC64LE
 int LZ4_decompress_fast_usingDict(const char* source, char* dest, int originalSize, const char* dictStart, int dictSize)
 {
-    return LZ4_decompress_usingDict_generic(source, dest, 0, originalSize, 0, dictStart, dictSize);
-}
-
-/* debug function */
-LZ4_FORCE_O2_GCC_PPC64LE
-int LZ4_decompress_safe_forceExtDict(const char* source, char* dest, int compressedSize, int maxOutputSize, const char* dictStart, int dictSize)
-{
-    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, endOnInputSize, full, 0, usingExtDict, (BYTE*)dest, (const BYTE*)dictStart, dictSize);
+    if (dictSize==0 || dictStart+dictSize == dest)
+        return LZ4_decompress_fast(source, dest, originalSize);
+    return LZ4_decompress_fast_extDict(source, dest, originalSize, dictStart, dictSize);
 }
 
 
@@ -1780,16 +1857,4 @@ char* LZ4_slideInputBuffer (void* state)
     return (char *)(uptrval)((LZ4_stream_t*)state)->internal_donotuse.dictionary;
 }
 
-/* Obsolete streaming decompression functions */
-
-int LZ4_decompress_safe_withPrefix64k(const char* source, char* dest, int compressedSize, int maxOutputSize)
-{
-    return LZ4_decompress_generic(source, dest, compressedSize, maxOutputSize, endOnInputSize, full, 0, withPrefix64k, (BYTE*)dest - 64 KB, NULL, 64 KB);
-}
-
-int LZ4_decompress_fast_withPrefix64k(const char* source, char* dest, int originalSize)
-{
-    return LZ4_decompress_generic(source, dest, 0, originalSize, endOnOutputSize, full, 0, withPrefix64k, (BYTE*)dest - 64 KB, NULL, 64 KB);
-}
-
 #endif   /* LZ4_COMMONDEFS_ONLY */