1 files changed, 106 insertions, 0 deletions
diff --git a/src/utf8.c b/src/utf8.c
new file mode 100644
index 0000000..4bb3b35
--- /dev/null
+++ b/src/utf8.c
@@ -0,0 +1,106 @@
+#include <stdlib.h>
+#include "bstrlib.h"
+#include "debug.h"
+
+#define advance(s) \
+  s++; \
+  check(*s >> 6 == 0x02, "UTF-8 decode error on byte %x", *s);
+
+// Reads a unicode code point from a UTF8-encoded string, and
+// puts it in the pointer n. If something illegal
+// is encountered, 0xFFFD is emitted.
+// Returns a pointer to next position in string, or NULL if no
+// more characters remain.
+extern unsigned char * from_utf8(unsigned char * s, unsigned int *n)
+{
+  int x = 0;
+
+  if (*s == 0) {
+    return NULL;
+  } else if (*s < 0x80) {
+    x = *s;
+  } else if (*s >> 5 == 0x06) {
+    x = *s & 0x1F;
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+  } else if (*s >> 4 == 0x0E) {
+    x = *s & 0x0F;
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+  } else if (*s >> 3 == 0x1E) {
+    x = *s & 0x07;
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+  } else if (*s >> 2 == 0x3E) {
+    x = *s & 0x03;
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+    advance(s);
+    x = (x << 6) + (*s & 0x3F);
+   } else {
+    log_err("UTF-8 decode error on byte %x", *s);
+    goto error;
+  }
+  *n = x;
+  s++;
+  return s;
+ error:
+  *n = 0xFFFD;
+  return s;
+}
+
+// Converts the unicode code point c to UTF-8,
+// putting the result in dest.  Returns 0 on success, -1 on error.
+extern int to_utf8(unsigned int c, bstring dest)
+{
+  if (c < 0x80) {
+    bconchar(dest, c);
+  } else if (c < 0x800) {
+    bconchar(dest, 192 + c/64);
+    bconchar(dest, 128 + c%64);
+  } else if (c - 0xd800u < 0x800) {
+    goto error;
+  } else if (c < 0x10000) {
+    bconchar(dest, 224 + c / 4096);
+    bconchar(dest, 128 + c /64%64);
+    bconchar(dest, 128 + c%64);
+  } else if (c < 0x110000) {
+    bconchar(dest, 240 + c/262144);
+    bconchar(dest, 128 + c/4096%64);
+    bconchar(dest, 128 + c/64%64);
+    bconchar(dest, 128 + c%64);
+  } else {
+    goto error;
+  }
+  return 0;
+error:
+  return -1;
+}
+
+#define bufpush(x) \
+  check(to_utf8(x, buf) == 0, "UTF-8 encode error on code point  %04x", x)
+
+// Returns the case-folded version of the source string, or NULL on error.
+extern bstring case_fold(bstring source)
+{
+  unsigned char * s = source->data;
+  unsigned int c = 0;
+  bstring buf = bfromcstr("");
+  while ((s = from_utf8(s, &c))) {
+#include "case_fold_switch.c"
+  }
+  return buf;
+error:
+  return NULL;
+}
+