From a123725a12e948d78badb2cb686d38548f1c633b Mon Sep 17 00:00:00 2001
From: Albert Cervin <albert@acervin.com>
Date: Thu, 6 Apr 2023 23:23:46 +0200
Subject: Implement window handling

Also implement searching.

fix undo boundaries

when it checked for other save point, it used && instead of == which
caused it to overwrite other types.

Fix bytes vs chars bug in text_get_region
---
 src/dged/utf8.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 src/dged/utf8.c

(limited to 'src/dged/utf8.c')

diff --git a/src/dged/utf8.c b/src/dged/utf8.c
new file mode 100644
index 0000000..abf5ef7
--- /dev/null
+++ b/src/dged/utf8.c
@@ -0,0 +1,67 @@
+#include "utf8.h"
+
+#include <stdio.h>
+
+bool utf8_byte_is_unicode_start(uint8_t byte) { return (byte & 0xc0) == 0xc0; }
+bool utf8_byte_is_unicode_continuation(uint8_t byte) {
+  return utf8_byte_is_unicode(byte) && !utf8_byte_is_unicode_start(byte);
+}
+bool utf8_byte_is_unicode(uint8_t byte) { return (byte & 0x80) != 0x0; }
+bool utf8_byte_is_ascii(uint8_t byte) { return !utf8_byte_is_unicode(byte); }
+
+uint32_t utf8_nbytes_in_char(uint8_t byte) {
+  // length of char is the number of leading ones
+  // flip it and count number of leading zeros
+  uint8_t invb = ~byte;
+  return __builtin_clz((uint32_t)invb) - 24;
+}
+
+// TODO: grapheme clusters, this returns the number of unicode code points
+uint32_t utf8_nchars(uint8_t *bytes, uint32_t nbytes) {
+  uint32_t nchars = 0;
+  uint32_t expected = 0;
+  for (uint32_t bi = 0; bi < nbytes; ++bi) {
+    uint8_t byte = bytes[bi];
+    if (utf8_byte_is_unicode(byte)) {
+      if (utf8_byte_is_unicode_start(byte)) {
+        expected = utf8_nbytes_in_char(byte) - 1;
+      } else { // continuation byte
+        --expected;
+        if (expected == 0) {
+          ++nchars;
+        }
+      }
+    } else { // ascii
+      ++nchars;
+    }
+  }
+  return nchars;
+}
+
+// TODO: grapheme clusters, this uses the number of unicode code points
+uint32_t utf8_nbytes(uint8_t *bytes, uint32_t nbytes, uint32_t nchars) {
+
+  uint32_t bi = 0;
+  uint32_t chars = 0;
+  uint32_t expected = 0;
+
+  while (chars < nchars && bi < nbytes) {
+    uint8_t byte = bytes[bi];
+    if (utf8_byte_is_unicode(byte)) {
+      if (utf8_byte_is_unicode_start(byte)) {
+        expected = utf8_nbytes_in_char(byte) - 1;
+      } else { // continuation char
+        --expected;
+        if (expected == 0) {
+          ++chars;
+        }
+      }
+    } else { // ascii
+      ++chars;
+    }
+
+    ++bi;
+  }
+
+  return bi;
+}
-- 
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