1 files changed, 107 insertions, 0 deletions
diff --git a/ext/misc/compress.c b/ext/misc/compress.c
new file mode 100644
index 0000000..a405911
--- /dev/null
+++ b/ext/misc/compress.c
@@ -0,0 +1,107 @@
+/*
+** 2014-06-13
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This SQLite extension implements SQL compression functions
+** compress() and uncompress() using ZLIB.
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <zlib.h>
+
+/*
+** Implementation of the "compress(X)" SQL function.  The input X is
+** compressed using zLib and the output is returned.
+**
+** The output is a BLOB that begins with a variable-length integer that
+** is the input size in bytes (the size of X before compression).  The
+** variable-length integer is implemented as 1 to 5 bytes.  There are
+** seven bits per integer stored in the lower seven bits of each byte.
+** More significant bits occur first.  The most significant bit (0x80)
+** is a flag to indicate the end of the integer.
+*/
+static void compressFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *pIn;
+  unsigned char *pOut;
+  unsigned int nIn;
+  unsigned long int nOut;
+  unsigned char x[8];
+  int i, j;
+
+  pIn = sqlite3_value_blob(argv[0]);
+  nIn = sqlite3_value_bytes(argv[0]);
+  nOut = 13 + nIn + (nIn+999)/1000;
+  pOut = sqlite3_malloc( nOut+5 );
+  for(i=4; i>=0; i--){
+    x[i] = (nIn >> (7*(4-i)))&0x7f;
+  }
+  for(i=0; i<4 && x[i]==0; i++){}
+  for(j=0; i<=4; i++, j++) pOut[j] = x[i];
+  pOut[j-1] |= 0x80;
+  compress(&pOut[j], &nOut, pIn, nIn);
+  sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free);
+}
+
+/*
+** Implementation of the "uncompress(X)" SQL function.  The argument X
+** is a blob which was obtained from compress(Y).  The output will be
+** the value Y.
+*/
+static void uncompressFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const unsigned char *pIn;
+  unsigned char *pOut;
+  unsigned int nIn;
+  unsigned long int nOut;
+  int rc;
+  int i;
+
+  pIn = sqlite3_value_blob(argv[0]);
+  nIn = sqlite3_value_bytes(argv[0]);
+  nOut = 0;
+  for(i=0; i<nIn && i<5; i++){
+    nOut = (nOut<<7) | (pIn[i]&0x7f);
+    if( (pIn[i]&0x80)!=0 ){ i++; break; }
+  }
+  pOut = sqlite3_malloc( nOut+1 );
+  rc = uncompress(pOut, &nOut, &pIn[i], nIn-i);
+  if( rc==Z_OK ){
+    sqlite3_result_blob(context, pOut, nOut, sqlite3_free);
+  }
+}
+
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_compress_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  int rc = SQLITE_OK;
+  SQLITE_EXTENSION_INIT2(pApi);
+  (void)pzErrMsg;  /* Unused parameter */
+  rc = sqlite3_create_function(db, "compress", 1, SQLITE_UTF8, 0,
+                               compressFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "uncompress", 1, SQLITE_UTF8, 0,
+                                 uncompressFunc, 0, 0);
+  }
+  return rc;
+}