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-rw-r--r--libbb/percent_decode.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/libbb/percent_decode.c b/libbb/percent_decode.c
new file mode 100644
index 0000000..9a9d80c
--- /dev/null
+++ b/libbb/percent_decode.c
@@ -0,0 +1,69 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+//kbuild:lib-y += percent_decode.o
+
+#include "libbb.h"
+
+static unsigned hex_to_bin(unsigned char c)
+{
+ unsigned v;
+
+ v = c - '0';
+ if (v <= 9)
+ return v;
+ /* c | 0x20: letters to lower case, non-letters
+ * to (potentially different) non-letters */
+ v = (unsigned)(c | 0x20) - 'a';
+ if (v <= 5)
+ return v + 10;
+ return ~0;
+/* For testing:
+void t(char c) { printf("'%c'(%u) %u\n", c, c, hex_to_bin(c)); }
+int main() { t(0x10); t(0x20); t('0'); t('9'); t('A'); t('F'); t('a'); t('f');
+t('0'-1); t('9'+1); t('A'-1); t('F'+1); t('a'-1); t('f'+1); return 0; }
+*/
+}
+
+char* FAST_FUNC percent_decode_in_place(char *str, int strict)
+{
+ /* note that decoded string is always shorter than original */
+ char *src = str;
+ char *dst = str;
+ char c;
+
+ while ((c = *src++) != '\0') {
+ unsigned v;
+
+ if (!strict && c == '+') {
+ *dst++ = ' ';
+ continue;
+ }
+ if (c != '%') {
+ *dst++ = c;
+ continue;
+ }
+ v = hex_to_bin(src[0]);
+ if (v > 15) {
+ bad_hex:
+ if (strict)
+ return NULL;
+ *dst++ = '%';
+ continue;
+ }
+ v = (v * 16) | hex_to_bin(src[1]);
+ if (v > 255)
+ goto bad_hex;
+ if (strict && (v == '/' || v == '\0')) {
+ /* caller takes it as indication of invalid
+ * (dangerous wrt exploits) chars */
+ return str + 1;
+ }
+ *dst++ = v;
+ src += 2;
+ }
+ *dst = '\0';
+ return str;
+}