Add utf8.{c,h} for common UTF-8 util functions

We need to validate some UTF-8, so this adds an is_valid_utf8()
function, which is probably pretty slow but should work correctly.

Signed-off-by: Ran Benita <ran234@gmail.com>

1 files changed, 142 insertions, 0 deletions

diff --git a/src/utf8.c b/src/utf8.c
new file mode 100644
index 0000000..11382c8
--- /dev/null
+++ b/src/utf8.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright © 2012 Intel Corporation
+ * Copyright © 2014 Ran Benita <ran234@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Author: Rob Bradford <rob@linux.intel.com>
+ */
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <inttypes.h>
+
+#include "utf8.h"
+
+int
+utf32_to_utf8(uint32_t unichar, char *buffer)
+{
+    int count, shift, length;
+    uint8_t head;
+
+    if (unichar <= 0x007f) {
+        buffer[0] = unichar;
+        buffer[1] = '\0';
+        return 2;
+    }
+    else if (unichar <= 0x07FF) {
+        length = 2;
+        head = 0xc0;
+    }
+    else if (unichar <= 0xffff) {
+        length = 3;
+        head = 0xe0;
+    }
+    else if (unichar <= 0x1fffff) {
+        length = 4;
+        head = 0xf0;
+    }
+    else if (unichar <= 0x3ffffff) {
+        length = 5;
+        head = 0xf8;
+    }
+    else {
+        length = 6;
+        head = 0xfc;
+    }
+
+    for (count = length - 1, shift = 0; count > 0; count--, shift += 6)
+        buffer[count] = 0x80 | ((unichar >> shift) & 0x3f);
+
+    buffer[0] = head | ((unichar >> shift) & 0x3f);
+    buffer[length] = '\0';
+
+    return length + 1;
+}
+
+bool
+is_valid_utf8(const char *ss, size_t len)
+{
+    size_t i = 0;
+    size_t tail_bytes = 0;
+    const uint8_t *s = (const uint8_t *) ss;
+
+    /* This beauty is from:
+     *  The Unicode Standard Version 6.2 - Core Specification, Table 3.7
+     *  http://www.unicode.org/versions/Unicode6.2.0/ch03.pdf#G7404
+     * We can optimize if needed. */
+    while (i < len)
+    {
+        if (s[i] <= 0x7F) {
+            tail_bytes = 0;
+        }
+        else if (s[i] >= 0xC2 && s[i] <= 0xDF) {
+            tail_bytes = 1;
+        }
+        else if (s[i] == 0xE0) {
+            i++;
+            if (i >= len || !(s[i] >= 0xA0 && s[i] <= 0xBF))
+                return false;
+            tail_bytes = 1;
+        }
+        else if (s[i] >= 0xE1 && s[i] <= 0xEC) {
+            tail_bytes = 2;
+        }
+        else if (s[i] == 0xED) {
+            i++;
+            if (i >= len || !(s[i] >= 0x80 && s[i] <= 0x9F))
+                return false;
+            tail_bytes = 1;
+        }
+        else if (s[i] >= 0xEE && s[i] <= 0xEF) {
+            tail_bytes = 2;
+        }
+        else if (s[i] == 0xF0) {
+            i++;
+            if (i >= len || !(s[i] >= 0x90 && s[i] <= 0xBF))
+                return false;
+            tail_bytes = 2;
+        }
+        else if (s[i] >= 0xF1 && s[i] <= 0xF3) {
+            tail_bytes = 3;
+        }
+        else if (s[i] == 0xF4) {
+            i++;
+            if (i >= len || !(s[i] >= 0x80 && s[i] <= 0x8F))
+                return false;
+            tail_bytes = 2;
+        }
+        else {
+            return false;
+        }
+
+        i++;
+
+        while (i < len && tail_bytes > 0 && s[i] >= 0x80 && s[i] <= 0xBF) {
+            i++;
+            tail_bytes--;
+        }
+
+        if (tail_bytes != 0)
+            return false;
+    }
+
+    return true;
+}