From 8e7efe37645453fac5ca98f8a9837f34d14f75b6 Mon Sep 17 00:00:00 2001
From: drh <>
Date: Fri, 28 Apr 2023 17:38:35 +0000
Subject: Improvements to the accuracy of json_error().  Add the extension SQL
 functions random_json(SEED) and random_json5(SEED).

FossilOrigin-Name: 8d09dc1c45a8026b94f70273d064e47939f30cadedc17548b5a26ba054a8d3a7
---
 ext/misc/randomjson.c | 202 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 202 insertions(+)
 create mode 100644 ext/misc/randomjson.c

(limited to 'ext/misc/randomjson.c')

diff --git a/ext/misc/randomjson.c b/ext/misc/randomjson.c
new file mode 100644
index 000000000..3a6f545fe
--- /dev/null
+++ b/ext/misc/randomjson.c
@@ -0,0 +1,202 @@
+/*
+** 2023-04-28
+**
+** 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 a the random_json(SEED) and
+** random_json5(SEED) functions.  Given a numeric SEED value, these
+** routines generate pseudo-random JSON or JSON5, respectively.  The
+** same value is always generated for the same seed.
+**
+** These SQL functions are intended for testing.  They do not have any
+** practical real-world use, that we know of.
+**
+** COMPILE:
+**
+**     gcc --shared -fPIC -o randomjson.so -I. ext/misc/randomjson.c
+**
+** USING FROM THE CLI:
+**
+**     .load ./randomjson
+**     SELECT random_json(1);
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+
+/* Pseudo-random number generator */
+typedef struct Prng {
+  unsigned int x, y;
+} Prng;
+
+/* Reseed the PRNG */
+static void prngSeed(Prng *p, unsigned int iSeed){
+  p->x = iSeed | 1;
+  p->y = iSeed;
+}
+
+/* Extract a random number */
+static unsigned int prngInt(Prng *p){
+  p->x = (p->x>>1) ^ ((1+~(p->x&1)) & 0xd0000001);
+  p->y = p->y*1103515245 + 12345;
+  return p->x ^ p->y;
+}
+
+static const char *azJsonAtoms[] = {
+  /* JSON                    /* JSON-5 */
+  "0",                       "0",
+  "1",                       "1",
+  "-1",                      "-1",
+  "2",                       "+2",
+  "3",                       "3",
+  "2.5",                     "2.5",
+  "0.75",                    ".75",
+  "-4.0e2",                  "-4.e2",
+  "5.0e-3",                  "+5e-3",
+  "0",                       "0x0",
+  "512",                     "0x200",
+  "256",                     "+0x100",
+  "-2748",                   "-0xabc",
+  "true",                    "true",
+  "false",                   "false",
+  "null",                    "null",
+  "9.0e999",                 "Infinity",
+  "-9.0e999",                "-Infinity",
+  "9.0e999",                 "+Infinity",
+  "null",                    "NaN",
+  "-0.0005123",              "-0.0005123",
+  "4.35e-3",                 "+4.35e-3",
+  "\"gem\\\"hay\"",          "\"gem\\\"hay\"",
+  "\"icy'joy\"",             "'icy\\'joy\'",
+  "\"keylog\"",              "\"key\\\nlog\"",
+  "\"mix\\\\\\tnet\"",       "\"mix\\\\\\tnet\"",
+  "{}",                      "{}",
+  "[]",                      "[]",
+  "[]",                      "[/*empty*/]",
+  "{}",                      "{//empty\n}",
+  "\"ask\"",                 "\"ask\"",
+  "\"bag\"",                 "\"bag\"",
+  "\"can\"",                 "\"can\"",
+  "\"day\"",                 "\"day\"",
+  "\"end\"",                 "'end'",
+  "\"fly\"",                 "\"fly\"",
+  "\"\"",                    "\"\"",
+};
+static const char *azJsonTemplate[] = {
+  /* JSON                                      JSON-5 */
+  "{\"a\":%,\"b\":%,\"c\":%}",                 "{a:%,b:%,c:%}",
+  "{\"a\":%,\"b\":%,\"c\":%,\"d\":%,\"e\":%}", "{a:%,b:%,c:%,d:%,e:%}",
+  "{\"a\":%,\"b\":%,\"c\":%,\"d\":%,\"\":%}",  "{a:%,b:%,c:%,d:%,\"\":%}",
+  "{\"d\":%}",                                 "{d:%}",
+  "{\"eeee\":%, \"ffff\":%}",                  "{eeee:% /*and*/, ffff:%}",
+  "{\"$g\":%,\"_h_\":%}",                      "{$g:%,_h_:%,}",
+  "{\"x\":%,\n  \"y\":%}",                     "{\"x\":%,\n  \"y\":%}",
+  "{\"a b c d\":%,\"e\":%,\"f\":%,\"x\":%,\"y\":%}",
+                                           "{\"a b c d\":%,e:%,f:%,x:%,y:%}",
+  "{\"Z\":%}",                                 "{Z:%,}",
+  "[%]",                                       "[%,]",
+  "[%,%]",                                     "[%,%]",
+  "[%,%,%]",                                   "[%,%,%,]",
+  "[%,%,%,%]",                                 "[%,%,%,%]",
+  "[%,%,%,%,%]",                               "[%,%,%,%,%]",
+};
+
+#define count(X)  (sizeof(X)/sizeof(X[0]))
+
+#define STRSZ 10000
+
+static void jsonExpand(
+  const char *zSrc,
+  char *zDest,
+  Prng *p,
+  int eType,            /* 0 for JSON, 1 for JSON5 */
+  unsigned int r        /* Growth probability 0..1000.  0 means no growth */
+){
+  unsigned int i, j, k;
+  const char *z;
+  size_t n;
+
+  j = 0;
+  if( zSrc==0 ){
+    k = prngInt(p)%(count(azJsonTemplate)/2);
+    k = k*2 + eType;
+    zSrc = azJsonTemplate[k];
+  }
+  if( strlen(zSrc)>=STRSZ/10 ) r = 0;
+  for(i=0; zSrc[i]; i++){
+    if( zSrc[i]!='%' ){
+      if( j<STRSZ ) zDest[j++] = zSrc[i];
+      continue;
+    }
+    if( r==0 || (r<1000 && (prngInt(p)%1000)<=r) ){
+      /* Fill in without values without any new % */
+      k = prngInt(p)%(count(azJsonAtoms)/2);
+      k = k*2 + eType;
+      z = azJsonAtoms[k];
+    }else{
+      /* Add new % terms */
+      k = prngInt(p)%(count(azJsonTemplate)/2);
+      k = k*2 + eType;
+      z = azJsonTemplate[k];
+    }
+    n = strlen(z);
+    if( j+n<STRSZ ){
+      memcpy(&zDest[j], z, n);
+      j += n;
+    }
+  }
+  zDest[STRSZ-1] = 0;
+  if( j<STRSZ ) zDest[j] = 0;
+}
+
+static void randJsonFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  unsigned int iSeed;
+  int eType = *(int*)sqlite3_user_data(context);
+  Prng prng;
+  char z1[STRSZ+1], z2[STRSZ+1];
+
+  iSeed = (unsigned int)sqlite3_value_int(argv[0]);
+  prngSeed(&prng, iSeed);
+  jsonExpand(0, z2, &prng, eType, 1000);
+  jsonExpand(z2, z1, &prng, eType, 1000);
+  jsonExpand(z1, z2, &prng, eType, 100);
+  jsonExpand(z2, z1, &prng, eType, 0);
+  sqlite3_result_text(context, z1, -1, SQLITE_TRANSIENT);
+}
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_randomjson_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  static int cOne = 1;
+  static int cZero = 0;
+  int rc = SQLITE_OK;
+  SQLITE_EXTENSION_INIT2(pApi);
+  (void)pzErrMsg;  /* Unused parameter */
+  rc = sqlite3_create_function(db, "random_json", 1,
+                   SQLITE_UTF8|SQLITE_INNOCUOUS|SQLITE_DETERMINISTIC,
+                   &cZero, randJsonFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "random_json5", 1,
+                   SQLITE_UTF8|SQLITE_INNOCUOUS|SQLITE_DETERMINISTIC,
+                   &cOne, randJsonFunc, 0, 0);
+  }
+  return rc;
+}
-- 
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