1 files changed, 108 insertions, 0 deletions
diff --git a/ext/misc/memtrace.c b/ext/misc/memtrace.c
new file mode 100644
index 0000000..19ff4c4
--- /dev/null
+++ b/ext/misc/memtrace.c
@@ -0,0 +1,108 @@
+/*
+** 2019-01-21
+**
+** 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 file implements an extension that uses the SQLITE_CONFIG_MALLOC
+** mechanism to add a tracing layer on top of SQLite.  If this extension
+** is registered prior to sqlite3_initialize(), it will cause all memory
+** allocation activities to be logged on standard output, or to some other
+** FILE specified by the initializer.
+**
+** This file needs to be compiled into the application that uses it.
+**
+** This extension is used to implement the --memtrace option of the
+** command-line shell.
+*/
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+/* The original memory allocation routines */
+static sqlite3_mem_methods memtraceBase;
+static FILE *memtraceOut;
+
+/* Methods that trace memory allocations */
+static void *memtraceMalloc(int n){
+  if( memtraceOut ){
+    fprintf(memtraceOut, "MEMTRACE: allocate %d bytes\n", 
+            memtraceBase.xRoundup(n));
+  }
+  return memtraceBase.xMalloc(n);
+}
+static void memtraceFree(void *p){
+  if( p==0 ) return;
+  if( memtraceOut ){
+    fprintf(memtraceOut, "MEMTRACE: free %d bytes\n", memtraceBase.xSize(p));
+  }
+  memtraceBase.xFree(p);
+}
+static void *memtraceRealloc(void *p, int n){
+  if( p==0 ) return memtraceMalloc(n);
+  if( n==0 ){
+    memtraceFree(p);
+    return 0;
+  }
+  if( memtraceOut ){
+    fprintf(memtraceOut, "MEMTRACE: resize %d -> %d bytes\n",
+            memtraceBase.xSize(p), memtraceBase.xRoundup(n));
+  }
+  return memtraceBase.xRealloc(p, n);
+}
+static int memtraceSize(void *p){
+  return memtraceBase.xSize(p);
+}
+static int memtraceRoundup(int n){
+  return memtraceBase.xRoundup(n);
+}
+static int memtraceInit(void *p){
+  return memtraceBase.xInit(p);
+}
+static void memtraceShutdown(void *p){
+  memtraceBase.xShutdown(p);
+}
+
+/* The substitute memory allocator */
+static sqlite3_mem_methods ersaztMethods = {
+  memtraceMalloc,
+  memtraceFree,
+  memtraceRealloc,
+  memtraceSize,
+  memtraceRoundup,
+  memtraceInit,
+  memtraceShutdown,
+  0
+};
+
+/* Begin tracing memory allocations to out. */
+int sqlite3MemTraceActivate(FILE *out){
+  int rc = SQLITE_OK;
+  if( memtraceBase.xMalloc==0 ){
+    rc = sqlite3_config(SQLITE_CONFIG_GETMALLOC, &memtraceBase);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &ersaztMethods);
+    }
+  }
+  memtraceOut = out;
+  return rc;
+}
+
+/* Deactivate memory tracing */
+int sqlite3MemTraceDeactivate(void){
+  int rc = SQLITE_OK;
+  if( memtraceBase.xMalloc!=0 ){
+    rc = sqlite3_config(SQLITE_CONFIG_MALLOC, &memtraceBase);
+    if( rc==SQLITE_OK ){
+      memset(&memtraceBase, 0, sizeof(memtraceBase));
+    }
+  }
+  memtraceOut = 0;
+  return rc;
+}