utils: Add function for strict str to int conversion

Define the u_readlong() function as a wrapper for strtol(). It performs
stricter checks on the input value and let the caller specify an interval
of acceptable values.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>

1 files changed, 21 insertions, 0 deletions

diff --git a/accel-pppd/utils.c b/accel-pppd/utils.c
index 491e650..a6a76c9 100644
--- a/accel-pppd/utils.c
+++ b/accel-pppd/utils.c
@@ -1,4 +1,6 @@
+#include <errno.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 #include "triton.h"
 #include "utils.h"
@@ -9,3 +11,22 @@ void __export u_inet_ntoa(in_addr_t addr, char *str)
 {
 	sprintf(str, "%i.%i.%i.%i", addr & 0xff, (addr >> 8) & 0xff, (addr >> 16) & 0xff, (addr >> 24) & 0xff);
 }
+
+int __export u_readlong(long int *dst, const char *src,
+                        long int min, long int max)
+{
+        char *src_stop = NULL;
+        long int rv;
+
+        if (dst == NULL || src == NULL || src[0] == '\0')
+                return -1;
+
+        errno = 0;
+        rv = strtol(src, &src_stop, 0);
+        if (errno != 0 || *src_stop != '\0' || rv < min || rv > max) {
+                return -1;
+        } else {
+                *dst = rv;
+                return 0;
+        }
+}