cembed

commit 5556aa64bbea0da9e3b46ec492a90c8f2225b446
parent b1fcd99ec975069313fc7bbee2fe56c0298e2586
Author: Robert Russell <robert@rr3.xyz>
Date:   Sat, 28 Dec 2024 13:54:32 -0800

Fix handling of binary data

Diffstat:
M
cembed.c
 | 
43
+++++++++++++++++++++++++++++--------------

1 file changed, 29 insertions(+), 14 deletions(-)
diff --git a/cembed.c b/cembed.c
@@ -6,10 +6,9 @@
 #define USAGE "usage: %s [-h|--help] NAME PATH\n"
 
 usize
-format_char(char *buf, char c) {
-	// Escape specials
-	switch (c) {
-	case '\0': strcpy(buf, "\\0");  return 2;
+format_char(char *buf, uchar curr, uchar next) {
+	// Escape specials.
+	switch (curr) {
 	case '\a': strcpy(buf, "\\a");  return 2;
 	case '\b': strcpy(buf, "\\b");  return 2;
 	case '\t': strcpy(buf, "\\t");  return 2;
@@ -22,20 +21,34 @@ format_char(char *buf, char c) {
 	case '\\': strcpy(buf, "\\\\"); return 2;
 	}
 
-	// Keep non-special printable ASCII as-is
-	if (' ' <= c && c <= '~') {
-		buf[0] = c;
+	// Keep non-special printable ASCII as-is.
+	if (' ' <= curr && curr <= '~') {
+		buf[0] = curr;
 		buf[1] = '\0';
 		return 1;
 	}
 
-	// Hex-encode rest
+	// Octal-encode rest. We can't hex-encode, because C hex encoding is
+	// variable length.
+	char octal[4] = {
+		"01234567"[(curr >> 6) & 0x3],
+		"01234567"[(curr >> 3) & 0x7],
+		"01234567"[(curr >> 0) & 0x7],
+		'\0',
+	};
 	buf[0] = '\\';
-	buf[1] = 'x';
-	buf[2] = "0123456789abcdef"[((uchar)c >> 0) & 0xf];
-	buf[3] = "0123456789abcdef"[((uchar)c >> 4) & 0xf];
-	buf[4] = '\0';
-	return 4;
+	// We want the encoding to be as small as possible, but if the next
+	// character is an octal digit, than we must pad to 3 digits.
+	if (('0' <= next && next <= '7') || curr >= 64) {
+		strcpy(&buf[1], &octal[0]);
+		return 4;
+	} else if (curr >= 8) {
+		strcpy(&buf[1], &octal[1]);
+		return 3;
+	} else {
+		strcpy(&buf[1], &octal[2]);
+		return 2;
+	}
 }
 
 int
@@ -73,7 +86,9 @@ main(int argc, char **argv) {
 		}
 
 		char buf[5];
-		line_len += format_char(buf, data[i]);
+		uchar curr = data[i];
+		uchar next = i + 1 < size ? data[i + 1] : '\0';
+		line_len += format_char(buf, curr, next);
 
 		fputs(buf, stdout);
 	}