lib/string_helpers: introduce generic string_unescape

[~andy/linux] / lib / string_helpers.c

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 1cffc223bff52b7e153dff043ae9149073050934..ed5c1454dd6288aacf85e4ee7db5e2e3ee947627 100644 (file)
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -2,10 +2,12 @@
  * Helpers for formatting and printing strings
  *
  * Copyright 31 August 2008 James Bottomley
+ * Copyright (C) 2013, Intel Corporation
  */
 #include <linux/kernel.h>
 #include <linux/math64.h>
 #include <linux/export.h>
+#include <linux/ctype.h>
 #include <linux/string_helpers.h>
 
 /**
@@ -66,3 +68,134 @@ int string_get_size(u64 size, const enum string_size_units units,
        return 0;
 }
 EXPORT_SYMBOL(string_get_size);
+
+static bool unescape_space(char **src, char **dst)
+{
+       char *p = *dst, *q = *src;
+
+       switch (*q) {
+       case 'n':
+               *p = '\n';
+               break;
+       case 'r':
+               *p = '\r';
+               break;
+       case 't':
+               *p = '\t';
+               break;
+       case 'v':
+               *p = '\v';
+               break;
+       case 'f':
+               *p = '\f';
+               break;
+       default:
+               return false;
+       }
+       *dst += 1;
+       *src += 1;
+       return true;
+}
+
+static bool unescape_octal(char **src, char **dst)
+{
+       char *p = *dst, *q = *src;
+       u8 num;
+
+       if (isodigit(*q) == 0)
+               return false;
+
+       num = (*q++) & 7;
+       while (num < 32 && isodigit(*q) && (q - *src < 3)) {
+               num <<= 3;
+               num += (*q++) & 7;
+       }
+       *p = num;
+       *dst += 1;
+       *src = q;
+       return true;
+}
+
+static bool unescape_hex(char **src, char **dst)
+{
+       char *p = *dst, *q = *src;
+       int digit;
+       u8 num;
+
+       if (*q++ != 'x')
+               return false;
+
+       num = digit = hex_to_bin(*q++);
+       if (digit < 0)
+               return false;
+
+       digit = hex_to_bin(*q);
+       if (digit >= 0) {
+               q++;
+               num = (num << 4) | digit;
+       }
+       *p = num;
+       *dst += 1;
+       *src = q;
+       return true;
+}
+
+static bool unescape_special(char **src, char **dst)
+{
+       char *p = *dst, *q = *src;
+
+       switch (*q) {
+       case '\"':
+               *p = '\"';
+               break;
+       case '\\':
+               *p = '\\';
+               break;
+       case 'a':
+               *p = '\a';
+               break;
+       case 'e':
+               *p = '\e';
+               break;
+       default:
+               return false;
+       }
+       *dst += 1;
+       *src += 1;
+       return true;
+}
+
+int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
+{
+       char *out = dst;
+
+       while (*src && --size) {
+               if (src[0] == '\\' && src[1] != '\0' && size > 1) {
+                       src++;
+                       size--;
+
+                       if (flags & UNESCAPE_SPACE &&
+                                       unescape_space(&src, &out))
+                               continue;
+
+                       if (flags & UNESCAPE_OCTAL &&
+                                       unescape_octal(&src, &out))
+                               continue;
+
+                       if (flags & UNESCAPE_HEX &&
+                                       unescape_hex(&src, &out))
+                               continue;
+
+                       if (flags & UNESCAPE_SPECIAL &&
+                                       unescape_special(&src, &out))
+                               continue;
+
+                       *out++ = '\\';
+               }
+               *out++ = *src++;
+       }
+       *out = '\0';
+
+       return out - dst;
+}
+EXPORT_SYMBOL(string_unescape);