1 files changed, 80 insertions, 113 deletions

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 8f8c4417f228..1826c7407258 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -239,29 +239,21 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
 }
 EXPORT_SYMBOL(string_unescape);
 
-static int escape_passthrough(unsigned char c, char **dst, size_t *osz)
+static bool escape_passthrough(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (*osz < 1)
-                return -ENOMEM;
-
-        *out++ = c;
-
-        *dst = out;
-        *osz -= 1;
-
-        return 1;
+        if (out < end)
+                *out = c;
+        *dst = out + 1;
+        return true;
 }
 
-static int escape_space(unsigned char c, char **dst, size_t *osz)
+static bool escape_space(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
         unsigned char to;
 
-        if (*osz < 2)
-                return -ENOMEM;
-
         switch (c) {
         case '\n':
                 to = 'n';
@@ -279,26 +271,25 @@ static int escape_space(unsigned char c, char **dst, size_t *osz)
                 to = 'f';
                 break;
         default:
-                return 0;
+                return false;
         }
 
-        *out++ = '\\';
-        *out++ = to;
+        if (out < end)
+                *out = '\\';
+        ++out;
+        if (out < end)
+                *out = to;
+        ++out;
 
         *dst = out;
-        *osz -= 2;
-
-        return 1;
+        return true;
 }
 
-static int escape_special(unsigned char c, char **dst, size_t *osz)
+static bool escape_special(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
         unsigned char to;
 
-        if (*osz < 2)
-                return -ENOMEM;
-
         switch (c) {
         case '\\':
                 to = '\\';
@@ -310,71 +301,78 @@ static int escape_special(unsigned char c, char **dst, size_t *osz)
                 to = 'e';
                 break;
         default:
-                return 0;
+                return false;
         }
 
-        *out++ = '\\';
-        *out++ = to;
+        if (out < end)
+                *out = '\\';
+        ++out;
+        if (out < end)
+                *out = to;
+        ++out;
 
         *dst = out;
-        *osz -= 2;
-
-        return 1;
+        return true;
 }
 
-static int escape_null(unsigned char c, char **dst, size_t *osz)
+static bool escape_null(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (*osz < 2)
-                return -ENOMEM;
-
         if (c)
-                return 0;
+                return false;
 
-        *out++ = '\\';
-        *out++ = '0';
+        if (out < end)
+                *out = '\\';
+        ++out;
+        if (out < end)
+                *out = '0';
+        ++out;
 
         *dst = out;
-        *osz -= 2;
-
-        return 1;
+        return true;
 }
 
-static int escape_octal(unsigned char c, char **dst, size_t *osz)
+static bool escape_octal(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (*osz < 4)
-                return -ENOMEM;
-
-        *out++ = '\\';
-        *out++ = ((c >> 6) & 0x07) + '0';
-        *out++ = ((c >> 3) & 0x07) + '0';
-        *out++ = ((c >> 0) & 0x07) + '0';
+        if (out < end)
+                *out = '\\';
+        ++out;
+        if (out < end)
+                *out = ((c >> 6) & 0x07) + '0';
+        ++out;
+        if (out < end)
+                *out = ((c >> 3) & 0x07) + '0';
+        ++out;
+        if (out < end)
+                *out = ((c >> 0) & 0x07) + '0';
+        ++out;
 
         *dst = out;
-        *osz -= 4;
-
-        return 1;
+        return true;
 }
 
-static int escape_hex(unsigned char c, char **dst, size_t *osz)
+static bool escape_hex(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (*osz < 4)
-                return -ENOMEM;
-
-        *out++ = '\\';
-        *out++ = 'x';
-        *out++ = hex_asc_hi(c);
-        *out++ = hex_asc_lo(c);
+        if (out < end)
+                *out = '\\';
+        ++out;
+        if (out < end)
+                *out = 'x';
+        ++out;
+        if (out < end)
+                *out = hex_asc_hi(c);
+        ++out;
+        if (out < end)
+                *out = hex_asc_lo(c);
+        ++out;
 
         *dst = out;
-        *osz -= 4;
-
-        return 1;
+        return true;
 }
 
 /**
@@ -426,19 +424,17 @@ static int escape_hex(unsigned char c, char **dst, size_t *osz)
  * it if needs.
  *
  * Return:
- * The amount of the characters processed to the destination buffer, or
- * %-ENOMEM if the size of buffer is not enough to put an escaped character is
- * returned.
- *
- * Even in the case of error @dst pointer will be updated to point to the byte
- * after the last processed character.
+ * The total size of the escaped output that would be generated for
+ * the given input and flags. To check whether the output was
+ * truncated, compare the return value to osz. There is room left in
+ * dst for a '\0' terminator if and only if ret < osz.
  */
-int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
+int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
                       unsigned int flags, const char *esc)
 {
-        char *out = *dst, *p = out;
+        char *p = dst;
+        char *end = p + osz;
         bool is_dict = esc && *esc;
-        int ret = 0;
 
         while (isz--) {
                 unsigned char c = *src++;
@@ -458,55 +454,26 @@ int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
                     (is_dict && !strchr(esc, c))) {
                         /* do nothing */
                 } else {
-                        if (flags & ESCAPE_SPACE) {
-                                ret = escape_space(c, &p, &osz);
-                                if (ret < 0)
-                                        break;
-                                if (ret > 0)
-                                        continue;
-                        }
-
-                        if (flags & ESCAPE_SPECIAL) {
-                                ret = escape_special(c, &p, &osz);
-                                if (ret < 0)
-                                        break;
-                                if (ret > 0)
-                                        continue;
-                        }
-
-                        if (flags & ESCAPE_NULL) {
-                                ret = escape_null(c, &p, &osz);
-                                if (ret < 0)
-                                        break;
-                                if (ret > 0)
-                                        continue;
-                        }
+                        if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
+                                continue;
+
+                        if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
+                                continue;
+
+                        if (flags & ESCAPE_NULL && escape_null(c, &p, end))
+                                continue;
 
                         /* ESCAPE_OCTAL and ESCAPE_HEX always go last */
-                        if (flags & ESCAPE_OCTAL) {
-                                ret = escape_octal(c, &p, &osz);
-                                if (ret < 0)
-                                        break;
+                        if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
                                 continue;
-                        }
-                        if (flags & ESCAPE_HEX) {
-                                ret = escape_hex(c, &p, &osz);
-                                if (ret < 0)
-                                        break;
+
+                        if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
                                 continue;
-                        }
                 }
 
-                ret = escape_passthrough(c, &p, &osz);
-                if (ret < 0)
-                        break;
+                escape_passthrough(c, &p, end);
         }
 
-        *dst = p;
-
-        if (ret < 0)
-                return ret;
-
-        return p - out;
+        return p - dst;
 }
 EXPORT_SYMBOL(string_escape_mem);