Extract utf8.c

1 files changed, 69 insertions, 0 deletions

diff --git a/utf8.c b/utf8.c
new file mode 100644
index 0000000..49e1477
--- /dev/null
+++ b/utf8.c
@@ -0,0 +1,69 @@
+#include "utf8.h"
+
+size_t codepoint_to_utf8(const uint32_t codepoint, unsigned char buffer[4]) {
+  if (codepoint <= 0x7F) {
+    buffer[0] = codepoint;
+    return 1;
+  }
+  if (codepoint >= 0x80 && codepoint <= 0x07FF) {
+    buffer[0] = 0xC0 | (codepoint >> 6);
+    buffer[1] = 0x80 | (codepoint & 0x3F);
+    return 2;
+  }
+  if (codepoint >= 0x0800 && codepoint <= 0xFFFF) {
+    buffer[0] = 0xE0 | (codepoint >> 12);
+    buffer[1] = 0x80 | ((codepoint >> 6) & 0x3F);
+    buffer[2] = 0x80 | (codepoint & 0x3F);
+    return 3;
+  }
+
+  if (codepoint >= 0x10000 && codepoint <= 0x10FFFF) {
+    buffer[0] = 0xF0 | (codepoint >> 18);
+    buffer[1] = 0x80 | ((codepoint >> 12) & 0x3F);
+    buffer[2] = 0x80 | ((codepoint >> 6) & 0x3F);
+    buffer[3] = 0x80 | (codepoint & 0x3F);
+    return 4;
+  }
+  return 0;
+}
+
+bool utf8_to_codepoint(const unsigned char buffer[4], const size_t len,
+                       uint32_t *codepoint) {
+  *codepoint = 0;
+  if (len == 1 && buffer[0] <= 0x7F) {
+    *codepoint = buffer[0];
+    return true;
+  }
+  if (len == 2 && (buffer[0] >= 0xC0 && buffer[0] <= 0xDF) &&
+      (buffer[1] >= 0x80 && buffer[1] <= 0xBF)) {
+    *codepoint = buffer[0] & 0x1F;
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[1] & 0x3F);
+    return true;
+  }
+  if (len == 3 && (buffer[0] >= 0xE0 && buffer[0] <= 0xEF) &&
+      (buffer[1] >= 0x80 && buffer[1] <= 0xBF) &&
+      (buffer[2] >= 0x80 && buffer[2] <= 0xBF)) {
+    *codepoint = buffer[0] & 0xF;
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[1] & 0x3F);
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[2] & 0x3F);
+    return true;
+  }
+  if (len == 4 && (buffer[0] >= 0xF0 && buffer[0] <= 0xF7) &&
+      (buffer[1] >= 0x80 && buffer[1] <= 0xBF) &&
+      (buffer[2] >= 0x80 && buffer[2] <= 0xBF) &&
+      (buffer[3] >= 0x80 && buffer[3] <= 0xBF)) {
+    *codepoint = buffer[0] & 7;
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[1] & 0x3F);
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[2] & 0x3F);
+    *codepoint = *codepoint << 6;
+    *codepoint = *codepoint | (buffer[3] & 0x3F);
+    return true;
+  }
+
+  return false;
+}