1 files changed, 124 insertions, 0 deletions
diff --git a/ext/misc/sqlar.c b/ext/misc/sqlar.c
new file mode 100644
index 0000000..47cb68f
--- /dev/null
+++ b/ext/misc/sqlar.c
@@ -0,0 +1,124 @@
+/*
+** 2017-12-17
+**
+** 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.
+**
+******************************************************************************
+**
+** Utility functions sqlar_compress() and sqlar_uncompress(). Useful
+** for working with sqlar archives and used by the shell tool's built-in
+** sqlar support.
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <zlib.h>
+#include <assert.h>
+
+/*
+** Implementation of the "sqlar_compress(X)" SQL function.
+**
+** If the type of X is SQLITE_BLOB, and compressing that blob using
+** zlib utility function compress() yields a smaller blob, return the
+** compressed blob. Otherwise, return a copy of X.
+**
+** SQLar uses the "zlib format" for compressed content.  The zlib format
+** contains a two-byte identification header and a four-byte checksum at
+** the end.  This is different from ZIP which uses the raw deflate format.
+**
+** Future enhancements to SQLar might add support for new compression formats.
+** If so, those new formats will be identified by alternative headers in the
+** compressed data.
+*/
+static void sqlarCompressFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  assert( argc==1 );
+  if( sqlite3_value_type(argv[0])==SQLITE_BLOB ){
+    const Bytef *pData = sqlite3_value_blob(argv[0]);
+    uLong nData = sqlite3_value_bytes(argv[0]);
+    uLongf nOut = compressBound(nData);
+    Bytef *pOut;
+
+    pOut = (Bytef*)sqlite3_malloc(nOut);
+    if( pOut==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }else{
+      if( Z_OK!=compress(pOut, &nOut, pData, nData) ){
+        sqlite3_result_error(context, "error in compress()", -1);
+      }else if( nOut<nData ){
+        sqlite3_result_blob(context, pOut, nOut, SQLITE_TRANSIENT);
+      }else{
+        sqlite3_result_value(context, argv[0]);
+      }
+      sqlite3_free(pOut);
+    }
+  }else{
+    sqlite3_result_value(context, argv[0]);
+  }
+}
+
+/*
+** Implementation of the "sqlar_uncompress(X,SZ)" SQL function
+**
+** Parameter SZ is interpreted as an integer. If it is less than or
+** equal to zero, then this function returns a copy of X. Or, if
+** SZ is equal to the size of X when interpreted as a blob, also
+** return a copy of X. Otherwise, decompress blob X using zlib
+** utility function uncompress() and return the results (another
+** blob).
+*/
+static void sqlarUncompressFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  uLong nData;
+  uLongf sz;
+
+  assert( argc==2 );
+  sz = sqlite3_value_int(argv[1]);
+
+  if( sz<=0 || sz==(nData = sqlite3_value_bytes(argv[0])) ){
+    sqlite3_result_value(context, argv[0]);
+  }else{
+    const Bytef *pData= sqlite3_value_blob(argv[0]);
+    Bytef *pOut = sqlite3_malloc(sz);
+    if( Z_OK!=uncompress(pOut, &sz, pData, nData) ){
+      sqlite3_result_error(context, "error in uncompress()", -1);
+    }else{
+      sqlite3_result_blob(context, pOut, sz, SQLITE_TRANSIENT);
+    }
+    sqlite3_free(pOut);
+  }
+}
+
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_sqlar_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, "sqlar_compress", 1, 
+                               SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
+                               sqlarCompressFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "sqlar_uncompress", 2,
+                                 SQLITE_UTF8|SQLITE_INNOCUOUS, 0,
+                                 sqlarUncompressFunc, 0, 0);
+  }
+  return rc;
+}