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[PATCH 09/13] Win32: reduce environment array reallocations

From
Stepan Kasal <kasal@ucw.cz>
Date
Jul 17, 2014, 15:38 UTC
Message-ID
<1405611486-10176-10-git-send-email-kasal@ucw.cz>
In-Reply-To
<1405611486-10176-1-git-send-email-kasal@ucw.cz>
From: Karsten Blees <blees@dcon.de>

Move environment array reallocation from do_putenv to the respective callers. Keep track of the environment size in a global variable. Use ALLOC_GROW in mingw_putenv to reduce reallocations. Allocate a sufficiently sized environment array in make_environment_block to prevent reallocations.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
---
 compat/mingw.c | 62 +++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 35 insertions(+), 27 deletions(-)
diff --git a/compat/mingw.c b/compat/mingw.c
index ffff592..e63fd6a 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -898,7 +898,12 @@ static char *path_lookup(const char *cmd, char **path, int exe_only)
 	return prog;
 }
 
-static char **do_putenv(char **env, const char *name, int free_old);
+static int do_putenv(char **env, const char *name, int size, int free_old);
+
+/* used number of elements of environ array, including terminating NULL */
+static int environ_size = 0;
+/* allocated size of environ array, in bytes */
+static int environ_alloc = 0;
 
 static int compareenv(const void *a, const void *b)
 {
@@ -914,31 +919,28 @@ static int compareenv(const void *a, const void *b)
 static wchar_t *make_environment_block(char **deltaenv)
 {
 	wchar_t *wenvblk = NULL;
-	int count = 0;
-	char **e, **tmpenv;
-	int size = 0, wenvsz = 0, wenvpos = 0;
+	char **tmpenv;
+	int i = 0, size = environ_size, wenvsz = 0, wenvpos = 0;
 
-	while (environ[count])
-		count++;
+	while (deltaenv && deltaenv[i])
+		i++;
 
-	/* copy the environment */
-	tmpenv = xmalloc(sizeof(*tmpenv) * (count + 1));
-	memcpy(tmpenv, environ, sizeof(*tmpenv) * (count + 1));
+	/* copy the environment, leaving space for changes */
+	tmpenv = xmalloc((size + i) * sizeof(char*));
+	memcpy(tmpenv, environ, size * sizeof(char*));
 
 	/* merge supplied environment changes into the temporary environment */
-	for (e = deltaenv; e && *e; e++)
-		tmpenv = do_putenv(tmpenv, *e, 0);
+	for (i = 0; deltaenv && deltaenv[i]; i++)
+		size = do_putenv(tmpenv, deltaenv[i], size, 0);
 
 	/* environment must be sorted */
-	for (count = 0; tmpenv[count]; )
-		count++;
-	qsort(tmpenv, count, sizeof(*tmpenv), compareenv);
+	qsort(tmpenv, size - 1, sizeof(char*), compareenv);
 
 	/* create environment block from temporary environment */
-	for (e = tmpenv; *e; e++) {
-		size = 2 * strlen(*e) + 2; /* +2 for final \0 */
+	for (i = 0; tmpenv[i]; i++) {
+		size = 2 * strlen(tmpenv[i]) + 2; /* +2 for final \0 */
 		ALLOC_GROW(wenvblk, (wenvpos + size) * sizeof(wchar_t), wenvsz);
-		wenvpos += xutftowcs(&wenvblk[wenvpos], *e, size) + 1;
+		wenvpos += xutftowcs(&wenvblk[wenvpos], tmpenv[i], size) + 1;
 	}
 	/* add final \0 terminator */
 	wenvblk[wenvpos] = 0;
@@ -1205,19 +1207,19 @@ static int lookupenv(char **env, const char *name, size_t nmln)
 
 /*
  * If name contains '=', then sets the variable, otherwise it unsets it
+ * Size includes the terminating NULL. Env must have room for size + 1 entries
+ * (in case of insert). Returns the new size. Optionally frees removed entries.
  */
-static char **do_putenv(char **env, const char *name, int free_old)
+static int do_putenv(char **env, const char *name, int size, int free_old)
 {
 	char *eq = strchrnul(name, '=');
 	int i = lookupenv(env, name, eq-name);
 
 	if (i < 0) {
 		if (*eq) {
-			for (i = 0; env[i]; i++)
-				;
-			env = xrealloc(env, (i+2)*sizeof(*env));
-			env[i] = (char*) name;
-			env[i+1] = NULL;
+			env[size - 1] = (char*) name;
+			env[size] = NULL;
+			size++;
 		}
 	}
 	else {
@@ -1225,11 +1227,13 @@ static char **do_putenv(char **env, const char *name, int free_old)
 			free(env[i]);
 		if (*eq)
 			env[i] = (char*) name;
-		else
+		else {
 			for (; env[i]; i++)
 				env[i] = env[i+1];
+			size--;
+		}
 	}
-	return env;
+	return size;
 }
 
 #undef getenv
@@ -1247,7 +1251,8 @@ char *mingw_getenv(const char *name)
 
 int mingw_putenv(const char *namevalue)
 {
-	environ = do_putenv(environ, namevalue, 1);
+	ALLOC_GROW(environ, (environ_size + 1) * sizeof(char*), environ_alloc);
+	environ_size = do_putenv(environ, namevalue, environ_size, 1);
 	return 0;
 }
 
@@ -2047,7 +2052,9 @@ void mingw_startup()
 		maxlen = max(maxlen, wcslen(wenv[i]));
 
 	/* nedmalloc can't free CRT memory, allocate resizable environment list */
-	environ = xcalloc(i + 1, sizeof(char*));
+	environ = NULL;
+	environ_size = i + 1;
+	ALLOC_GROW(environ, environ_size * sizeof(char*), environ_alloc);
 
 	/* allocate buffer (wchar_t encodes to max 3 UTF-8 bytes) */
 	maxlen = 3 * maxlen + 1;
@@ -2064,6 +2071,7 @@ void mingw_startup()
 		len = xwcstoutf(buffer, wenv[i], maxlen);
 		environ[i] = xmemdupz(buffer, len);
 	}
+	environ[i] = NULL;
 	free(buffer);
 
 	/* initialize critical section for waitpid pinfo_t list */

-- 
2.0.0.9635.g0be03cb

-- 
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Previous: Stepan KasalNext: Stepan Kasal
Message 12 of 23 in “mingw unicode environment”
  1. 00/13 mingw unicode environmentStepan Kasal, Jul 17, 2014
  2. 01/13 Revert "Windows: teach getenv to do a case-sensitive search"Stepan Kasal, Jul 17, 2014
  3. 02/13 Win32: Unicode environment (outgoing)Stepan Kasal, Jul 17, 2014
  4. fixup! Win32: Unicode environment (outgoing)Karsten Blees, Jul 19, 2014
  5. Junio C HamanoJul 21, 2014
  6. 03/13 Win32: Unicode environment (incoming)Stepan Kasal, Jul 17, 2014
  7. 04/13 Win32: fix environment memory leaksStepan Kasal, Jul 17, 2014
  8. 05/13 Win32: unify environment case-sensitivityStepan Kasal, Jul 17, 2014
  9. 06/13 Win32: unify environment function namesStepan Kasal, Jul 17, 2014
  10. 07/13 Win32: factor out environment block creationStepan Kasal, Jul 17, 2014
  11. 08/13 Win32: don't copy the environment twice when spawning child processesStepan Kasal, Jul 17, 2014
  12. 09/13 Win32: reduce environment array reallocationsStepan Kasal, Jul 17, 2014
  13. 10/13 Win32: use low-level memory allocation during initializationStepan Kasal, Jul 17, 2014
  14. 11/13 Win32: keep the environment sortedStepan Kasal, Jul 17, 2014
  15. 12/13 Win32: patch Windows environment on startupStepan Kasal, Jul 17, 2014
  16. 13/13 Enable color output in Windows cmd.exeStepan Kasal, Jul 17, 2014
  17. Junio C HamanoJul 17, 2014
  18. Karsten BleesJul 17, 2014
  19. Junio C HamanoJul 17, 2014
  20. Stepan KasalJul 17, 2014
  21. Junio C HamanoJul 17, 2014
  22. Karsten BleesJul 17, 2014
  23. Stepan KasalJul 18, 2014

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