Add new string to long long function

src/redis.h

@@ -894,6 +894,7 @@ int stringmatchlen(const char *pattern, int patternLen,
 int stringmatch(const char *pattern, const char *string, int nocase);
 long long memtoll(const char *p, int *err);
 int ll2string(char *s, size_t len, long long value);
+int string2ll(char *s, size_t len, long long *value);
 int d2string(char *s, size_t len, double value);
 int isStringRepresentableAsLong(sds s, long *longval);
 int isStringRepresentableAsLongLong(sds s, long long *longval);

src/util.c

@@ -201,6 +201,63 @@ int ll2string(char *s, size_t len, long long value) {
     return l;
 }
 
+/* Convert a string into a long long. Returns 1 if the string could be parsed
+ * into a (non-overflowing) long long, 0 otherwise. The value will be set to
+ * the parsed value when appropriate. */
+int string2ll(char *s, size_t slen, long long *value) {
+    char *p = s;
+    size_t plen = 0;
+    int negative = 0;
+    unsigned long long v;
+
+    if (plen == slen)
+        return 0;
+
+    if (p[0] == '-') {
+        negative = 1;
+        p++; plen++;
+
+        /* Abort on only a negative sign. */
+        if (plen == slen)
+            return 0;
+    }
+
+    /* First digit should be 1-9. */
+    if (p[0] >= '1' && p[0] <= '9') {
+        v = p[0]-'0';
+        p++; plen++;
+    } else {
+        return 0;
+    }
+
+    while (plen < slen && p[0] >= '0' && p[0] <= '9') {
+        if (v > (ULLONG_MAX / 10)) /* Overflow. */
+            return 0;
+        v *= 10;
+
+        if (v > (ULLONG_MAX - (p[0]-'0'))) /* Overflow. */
+            return 0;
+        v += p[0]-'0';
+
+        p++; plen++;
+    }
+
+    /* Return if not all bytes were used. */
+    if (plen < slen)
+        return 0;
+
+    if (negative) {
+        if (v > (-(unsigned long long)LLONG_MIN)) /* Overflow. */
+            return 0;
+        if (value != NULL) *value = -v;
+    } else {
+        if (v > LLONG_MAX) /* Overflow. */
+            return 0;
+        if (value != NULL) *value = v;
+    }
+    return 1;
+}
+
 /* Convert a double to a string representation. Returns the number of bytes
  * required. The representation should always be parsable by stdtod(3). */
 int d2string(char *buf, size_t len, double value) {