[project @ 1998-02-02 17:27:26 by simonm]

[ghc-hetmet.git] / ghc / lib / posix / cbits / env.c

diff --git a/ghc/lib/posix/cbits/env.c b/ghc/lib/posix/cbits/env.c
new file mode 100644 (file)
index 0000000..936039c
--- /dev/null
+++ b/ghc/lib/posix/cbits/env.c
@@ -0,0 +1,165 @@
+/*
+%
+% (c) The GRASP/AQUA Project, Glasgow University, 1995-1996
+%
+\subsection[env.lc]{Environment Handling for LibPosix}
+
+Many useful environment functions are not necessarily provided by libc.
+To get around this problem, we introduce our own.  The first time that
+you modify your environment, we copy the environment wholesale into
+malloc'ed locations, so that subsequent modifications can do proper
+memory management.  The $environ$ variable is updated with a pointer
+to the current environment so that the normal $getenv$ and $exec*$ functions
+should continue to work properly.
+
+\begin{code}
+*/
+
+#include "rtsdefs.h"
+#include "libposix.h"
+
+/* Switch this on once we've moved the environment to the malloc arena */
+int dirtyEnv = 0;
+
+/* 
+ * For some reason, OSF turns off the prototype for this if we're
+ * _POSIX_SOURCE.  Seems to me that this ought to be an ANSI-ism
+ * rather than a POSIX-ism, but no matter.  (JSM(?))
+ */
+
+char *
+strDup(const char *src)
+{
+    int len = strlen(src) + 1;
+    char *dst;
+
+    if ((dst = malloc(len)) != NULL)
+       memcpy(dst, src, len);
+    return dst;
+}
+
+/* Replace the entire environment */
+int
+setenviron(char **envp)
+{
+    char **old = environ;
+    int dirtyOld = dirtyEnv;
+    int i;
+
+    /* A quick hack to move the strings out of the heap */
+    environ = envp;
+    if (copyenv() != 0) {
+       environ = old;
+       return -1;
+    }
+    /* Release the old space if we allocated it ourselves earlier */
+    if (dirtyOld) {
+       for (i = 0; old[i] != NULL; i++)
+           free(old[i]);
+       free(old);
+    }
+    return 0;
+}
+
+/* Copy initial environment into malloc arena */
+int
+copyenv(void)
+{
+    char **new;
+    int i;
+
+    for (i = 0; environ[i] != NULL; i++);
+
+    if ((new = (char **) malloc((i + 1) * sizeof(char *))) == NULL)
+        return -1;
+
+    new[i] = NULL;
+
+    while (--i >= 0) {
+       if ((new[i] = strDup(environ[i])) == NULL) {
+           while (new[++i] != NULL)
+               free(new[i]);
+           free(new);
+           return -1;
+       }
+    }
+    environ = new;
+    dirtyEnv = 1;
+    return 0;
+}
+
+/* Set or replace an environment variable 
+ * simonm 14/2/96 - this is different to the standard C library 
+ * implementation and the prototypes clash, so I'm calling it _setenv.
+ */
+int
+_setenv(char *mapping)
+{
+    int i, keylen;
+    char *p;
+    char **new;
+
+    /* We must have a non-empty key and an '=' */
+    if (mapping[0] == '=' || (p = strchr(mapping, '=')) == NULL) {
+       errno = EINVAL;
+       return -1;
+    }
+    /* Include through the '=' for matching */
+    keylen = p - mapping + 1;
+
+    if (!dirtyEnv && copyenv() != 0)
+       return -1;
+
+    if ((p = strDup(mapping)) == NULL)
+       return -1;
+
+    /* Look for an existing key that matches */
+    for (i = 0; environ[i] != NULL && strncmp(environ[i], p, keylen) != 0; i++);
+
+    if (environ[i] != NULL) {
+       free(environ[i]);
+       environ[i] = p;
+    } else {
+       if ((new = (char **) realloc(environ, (i + 1) * sizeof(char *))) == NULL) {
+           free(p);
+           return -1;
+       }
+       new[i] = p;
+       new[i + 1] = NULL;
+       environ = new;
+    }
+    return 0;
+}
+
+/* Delete a variable from the environment */
+int
+delenv(char *name)
+{
+    int i, keylen;
+
+    if (strchr(name, '=') != NULL) {
+       errno = EINVAL;
+       return -1;
+    }
+    keylen = strlen(name);
+
+    if (!dirtyEnv && copyenv() != 0)
+       return -1;
+
+    /* Look for a matching key */
+    for (i = 0; environ[i] != NULL &&
+      (strncmp(environ[i], name, keylen) != 0 || environ[i][keylen] != '='); i++);
+
+    /* Don't complain if it wasn't there to begin with */
+    if (environ[i] == NULL) {
+       return 0;
+    }
+    free(environ[i]);
+
+    do {
+       environ[i] = environ[i + 1];
+       i++;
+    } while (environ[i] != NULL);
+
+    return 0;
+}