Prototype implementation of the unistr() SQL function.

FossilOrigin-Name: 7cc302de05ed2a973372c05f55b048bf99af3d2590dd29f6fd0f379fb451aa0e

3 files changed, 137 insertions, 7 deletions

diff --git a/manifest b/manifest
index f2b2a13a5..6f0eef751 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Tamp\sdown\svarious\sharmless\scompiler\swarnings.\s\sUse\s"int"\sin\splaces\sinstead\nof\s"u16"\sor\s"i16"\ssince\sthe\scompiler\scomplains\sless\sand\sgenerates\sfaster\ncode.
-D 2025-02-22T16:44:14.174
+C Prototype\simplementation\sof\sthe\sunistr()\sSQL\sfunction.
+D 2025-02-22T23:18:38.072
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
@@ -735,7 +735,7 @@ F src/delete.c 03a77ba20e54f0f42ebd8eddf15411ed6bdb06a2c472ac4b6b336521bf7cea42
 F src/expr.c 6769d3f0ca9b1792e883e3ff21fdc5ca0033cece65571ebbf9d8b8fe2f47cd27
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c 928ed2517e8732113d2b9821aa37af639688d752f4ea9ac6e0e393d713eeb76f
-F src/func.c 6c8b7bbdc5b588f3cfc79ed5effcfd3031758f5034c464fcd8891e8010b4d317
+F src/func.c ddfb4f3b8d2fbbe46dbe2bb28c9c79fc1defb7855975dfd851f2dd8417cc70be
 F src/global.c a19e4b1ca1335f560e9560e590fc13081e21f670643367f99cb9e8f9dc7d615b
 F src/hash.c 73934a7f7ab1cb110614a9388cb516893b0cf5b7b69e4fd1a0780ac4ce166be7
 F src/hash.h 46b92795a95bfefb210f52f0c316e9d7cdbcdd7e7fcfb0d8be796d3a5767cddf
@@ -2210,8 +2210,11 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P eeea11278bdebe336f0c30fbad79e30e3456ab67dae46abdd5f9951ea1b61bed
-R 8078ee78be0e4d7d18ee35dbad7406fe
+P 742827f049768c4f69ccdfaadfad339aaad3bc126d3a68b90cfea01d825bf7ce
+R 487d823b2a97be800308516e5c94d276
+T *branch * unistr
+T *sym-unistr *
+T -sym-trunk *
 U drh
-Z 2ee0c7ad1f2d8a9853a04c1df0464ab5
+Z f399533fbf6bd526a1da3885c8fdaf47
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 5eab3882f..080a91b1b 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-742827f049768c4f69ccdfaadfad339aaad3bc126d3a68b90cfea01d825bf7ce
+7cc302de05ed2a973372c05f55b048bf99af3d2590dd29f6fd0f379fb451aa0e
diff --git a/src/func.c b/src/func.c
index 5784b75e2..c80ac915a 100644
--- a/src/func.c
+++ b/src/func.c
@@ -1150,6 +1150,132 @@ void sqlite3QuoteValue(StrAccum *pStr, sqlite3_value *pValue){
 }
 
 /*
+** Write a single UTF8 character whose value if v into the
+** buffer starting at zOut.  Return the number of bytes needed
+** to encode that character.
+*/
+static int appendOneUtf8Char(char *zOut, u32 v){
+  if( v<0x00080 ){
+    zOut[0] = (u8)(v & 0xff);
+    return 1;
+  }
+  if( v<0x00800 ){
+    zOut[0] = 0xc0 + (u8)((v>>6) & 0x1f);
+    zOut[1] = 0x80 + (u8)(v & 0x3f);
+    return 2;
+  }
+  if( v<0x10000 ){
+    zOut[0] = 0xe0 + (u8)((v>>12) & 0x0f);
+    zOut[1] = 0x80 + (u8)((v>>6) & 0x3f);
+    zOut[2] = 0x80 + (u8)(v & 0x3f);
+    return 3;
+  }
+  zOut[0] = 0xf0 + (u8)((v>>18) & 0x07);
+  zOut[1] = 0x80 + (u8)((v>>12) & 0x3f);
+  zOut[2] = 0x80 + (u8)((v>>6) & 0x3f);
+  zOut[3] = 0x80 + (u8)(v & 0x3f);
+  return 4;
+}
+
+/*
+** Return true if z[] begins with N hexadecimal digits, and write
+** a decoding of those digits into *pVal.  Or return false if any
+** one of the first N characters in z[] is not a hexadecimal digit.
+*/
+static int isNHex(const char *z, int N, u32 *pVal){
+  int i;
+  int v = 0;
+  for(i=0; i<N; i++){
+    if( !sqlite3Isxdigit(z[i]) ) return 0;
+    v = (v<<4) + sqlite3HexToInt(z[i]);
+  }
+  *pVal = v;
+  return 1;
+}
+
+/*
+** Implementation of the UNISTR() function.
+**
+** This is intended to be a work-alike of the UNISTR() function in
+** PostgreSQL.  Quoting from the PG documentation (PostgreSQL 17 -
+** scraped on 2025-02-22):
+**
+**    Evaluate escaped Unicode characters in the argument. Unicode
+**    characters can be specified as \XXXX (4 hexadecimal digits),
+**    \+XXXXXX (6 hexadecimal digits), \uXXXX (4 hexadecimal digits),
+**    or \UXXXXXXXX (8 hexadecimal digits). To specify a backslash,
+**    write two backslashes. All other characters are taken literally.
+*/
+static void unistrFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  char *zOut;
+  const char *zIn;
+  int nIn;
+  int i, j, n;
+  u32 v;
+
+  assert( argc==1 );
+  zIn = (const char*)sqlite3_value_text(argv[0]);
+  if( zIn==0 ) return;
+  nIn = sqlite3_value_bytes(argv[0]);
+  zOut = sqlite3_malloc64(nIn+1);
+  if( zOut==0 ){
+    sqlite3_result_error_nomem(context);
+    return;
+  }
+  i = j = 0;
+  while( i<nIn ){
+    char *z = strchr(&zIn[i],'\\');
+    if( z==0 ){
+      n = nIn - i;
+      memmove(&zOut[j], &zIn[i], n);
+      j += n;
+      break;
+    }
+    n = z - &zIn[i];
+    if( n>0 ){
+      memmove(&zOut[j], &zIn[i], n);
+      j += n;
+      i += n;
+    }
+    if( zIn[i+1]=='\\' ){
+      i += 2;
+      zOut[j++] = '\\';
+    }else if( sqlite3Isxdigit(zIn[i+1]) ){
+      if( !isNHex(&zIn[i+1], 4, &v) ) goto unistr_error;
+      i += 5;
+      j += appendOneUtf8Char(&zOut[j], v);
+    }else if( zIn[i+1]=='+' ){
+      if( !isNHex(&zIn[i+2], 6, &v) ) goto unistr_error;
+      i += 8;
+      j += appendOneUtf8Char(&zOut[j], v);
+    }else if( zIn[i+1]=='u' ){
+      if( !isNHex(&zIn[i+2], 4, &v) ) goto unistr_error;
+      i += 6;
+      j += appendOneUtf8Char(&zOut[j], v);
+    }else if( zIn[i+1]=='U' ){
+      if( !isNHex(&zIn[i+2], 8, &v) ) goto unistr_error;
+      i += 10;
+      j += appendOneUtf8Char(&zOut[j], v);
+    }else{
+      goto unistr_error;
+    }
+  }
+  zOut[j] = 0;
+  sqlite3_result_text64(context, zOut, j, sqlite3_free, SQLITE_UTF8);
+  return;
+
+unistr_error:
+  sqlite3_free(zOut);
+  sqlite3_result_error(context, "invalid Unicode escape", -1);
+  return;
+}
+
+
+/*
 ** Implementation of the QUOTE() function. 
 **
 ** The quote(X) function returns the text of an SQL literal which is the
@@ -2736,6 +2862,7 @@ void sqlite3RegisterBuiltinFunctions(void){
     DFUNCTION(sqlite_version,    0, 0, 0, versionFunc      ),
     DFUNCTION(sqlite_source_id,  0, 0, 0, sourceidFunc     ),
     FUNCTION(sqlite_log,         2, 0, 0, errlogFunc       ),
+    FUNCTION(unistr,             1, 0, 0, unistrFunc       ),
     FUNCTION(quote,              1, 0, 0, quoteFunc        ),
     VFUNCTION(last_insert_rowid, 0, 0, 0, last_insert_rowid),
     VFUNCTION(changes,           0, 0, 0, changes          ),