Implementation of UTF-8 ranges

New constructor 'lpeg.utfR(from, to)' creates a pattern that matches
UTF-8 byte sequences representing code points in the range [from, to].

1 files changed, 40 insertions, 0 deletions

diff --git a/lpvm.c b/lpvm.c
index 737418c..dbe1a8e 100644
--- a/lpvm.c
+++ b/lpvm.c
@@ -28,6 +28,35 @@ static const Instruction giveup = {{IGiveup, 0, 0}};
 
 
 /*
+** Decode one UTF-8 sequence, returning NULL if byte sequence is invalid.
+*/
+static const char *utf8_decode (const char *o, int *val) {
+  static const unsigned int limits[] = {0xFF, 0x7F, 0x7FF, 0xFFFFu};
+  const unsigned char *s = (const unsigned char *)o;
+  unsigned int c = s[0];  /* first byte */
+  unsigned int res = 0;  /* final result */
+  if (c < 0x80)  /* ascii? */
+    res = c;
+  else {
+    int count = 0;  /* to count number of continuation bytes */
+    while (c & 0x40) {  /* still have continuation bytes? */
+      int cc = s[++count];  /* read next byte */
+      if ((cc & 0xC0) != 0x80)  /* not a continuation byte? */
+        return NULL;  /* invalid byte sequence */
+      res = (res << 6) | (cc & 0x3F);  /* add lower 6 bits from cont. byte */
+      c <<= 1;  /* to test next bit */
+    }
+    res |= (c & 0x7F) << (count * 5);  /* add first byte */
+    if (count > 3 || res > 0x10FFFFu || res <= limits[count])
+      return NULL;  /* invalid byte sequence */
+    s += count;  /* skip continuation bytes read */
+  }
+  *val = res;
+  return (const char *)s + 1;  /* +1 to include first byte */
+}
+
+
+/*
 ** {======================================================
 ** Virtual Machine
 ** =======================================================
@@ -198,6 +227,17 @@ const char *match (lua_State *L, const char *o, const char *s, const char *e,
         else goto fail;
         continue;
       }
+      case IUTFR: {
+        int codepoint;
+        if (s >= e)
+          goto fail;
+        s = utf8_decode (s, &codepoint);
+        if (s && p[1].offset <= codepoint && codepoint <= utf_to(p))
+          p += 2;
+        else
+          goto fail;
+        continue;
+      }
       case ITestAny: {
         if (s < e) p += 2;
         else p += getoffset(p);