Remove unused conversion code from mbstring

Over the last few years, I refactored mbstring to perform encoding conversion
a buffer at a time, rather than a single byte at a time. This resulted in a
huge performance increase.

After the refactoring, the old "byte-at-a-time" code was retained for two
reasons:

1) It was used by the mailparse PECL extension.
2) It was used to implement mb_strcut for some text encodings.

However, after reviewing mailparse's use of mbstring, it is clear that
mailparse only relies on mbstring for decoding of QPrint, and possibly
Base64. It does not use the byte-at-a-time conversion code for any
other encoding.

Further, mb_strcut only relies on the byte-at-a-time conversion code
for a limited number of legacy text encodings, such as ISO-2022-JP,
HZ, UTF-7, etc.

Hence, we can remove over 5000 lines of unused code without breaking
anything. This will help to reduce binary size, and make the mbstring
codebase easier to navigate for new contributors.

Author: alexdowad

ext/mbstring/libmbfl/filters/mbfilter_cjk.c

@@ -42,8 +42,4 @@ int mbfilter_sjis_emoji_docomo2unicode(int s, int *snd);
 int mbfilter_sjis_emoji_kddi2unicode(int s, int *snd);
 int mbfilter_sjis_emoji_sb2unicode(int s, int *snd);
 
-int mbfilter_unicode2sjis_emoji_docomo(int c, int *s1, mbfl_convert_filter *filter);
-int mbfilter_unicode2sjis_emoji_kddi_sjis(int c, int *s1, mbfl_convert_filter *filter);
-int mbfilter_unicode2sjis_emoji_sb(int c, int *s1, mbfl_convert_filter *filter);
-
 #endif /* MBFL_MBFILTER_CJK_H */

ext/mbstring/libmbfl/filters/mbfilter_cjk.h

@@ -33,10 +33,5 @@
 #include "mbfilter.h"
 
 extern const mbfl_encoding mbfl_encoding_cp51932;
-extern const struct mbfl_convert_vtbl vtbl_cp51932_wchar;
-extern const struct mbfl_convert_vtbl vtbl_wchar_cp51932;
-
-int mbfl_filt_conv_cp51932_wchar(int c, mbfl_convert_filter *filter);
-int mbfl_filt_conv_wchar_cp51932(int c, mbfl_convert_filter *filter);
 
 #endif /* MBFL_MBFILTER_CP51932_H */

ext/mbstring/libmbfl/filters/mbfilter_cp51932.h

@@ -21,70 +21,19 @@ static inline uint32_t coalesce(uint32_t a, uint32_t b)
 	return a ? a : b;
 }
 
-/* Helper for single-byte encodings which use a conversion table */
-static int mbfl_conv_singlebyte_table(int c, mbfl_convert_filter *filter, int tbl_min, const unsigned short tbl[])
-{
-	if (c >= 0 && c < tbl_min) {
-		CK((*filter->output_function)(c, filter->data));
-	} else if (c < 0) {
-		CK((*filter->output_function)(MBFL_BAD_INPUT, filter->data));
-	} else {
-		CK((*filter->output_function)(coalesce(tbl[c - tbl_min], MBFL_BAD_INPUT), filter->data));
-	}
-	return 0;
-}
-
-static int mbfl_conv_reverselookup_table(int c, mbfl_convert_filter *filter, int tbl_min, const unsigned short tbl[])
-{
-	if (c >= 0 && c < tbl_min) {
-		CK((*filter->output_function)(c, filter->data));
-	} else if (c < 0 || c == MBFL_BAD_INPUT) {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	} else {
-		for (int i = 0; i < 256 - tbl_min; i++) {
-			if (c == tbl[i]) {
-				CK((*filter->output_function)(i + tbl_min, filter->data));
-				return 0;
-			}
-		}
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	}
-	return 0;
-}
-
 /* Initialize data structures for a single-byte encoding */
 #define DEF_SB(id, name, mime_name, aliases) \
-	static int mbfl_filt_conv_##id##_wchar(int c, mbfl_convert_filter *filter); \
-	static int mbfl_filt_conv_wchar_##id(int c, mbfl_convert_filter *filter); \
 	static size_t mb_##id##_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state); \
 	static void mb_wchar_to_##id(uint32_t *in, size_t len, mb_convert_buf *buf, bool end); \
-	static const struct mbfl_convert_vtbl vtbl_##id##_wchar = { \
-		mbfl_no_encoding_##id, \
-		mbfl_no_encoding_wchar, \
-		mbfl_filt_conv_common_ctor, \
-		NULL, \
-		mbfl_filt_conv_##id##_wchar, \
-		mbfl_filt_conv_common_flush, \
-		NULL \
-	}; \
-	static const struct mbfl_convert_vtbl vtbl_wchar_##id = { \
-		mbfl_no_encoding_wchar, \
-		mbfl_no_encoding_##id, \
-		mbfl_filt_conv_common_ctor, \
-		NULL, \
-		mbfl_filt_conv_wchar_##id, \
-		mbfl_filt_conv_common_flush, \
-		NULL \
-	}; \
 	const mbfl_encoding mbfl_encoding_##id = { \
 		mbfl_no_encoding_##id, \
 		name, \
 		mime_name, \
 		aliases, \
 		NULL, \
 		MBFL_ENCTYPE_SBCS, \
-		&vtbl_##id##_wchar, \
-		&vtbl_wchar_##id, \
+		NULL, \
+		NULL, \
 		mb_##id##_to_wchar, \
 		mb_wchar_to_##id, \
 		NULL, \
@@ -93,12 +42,6 @@ static int mbfl_conv_reverselookup_table(int c, mbfl_convert_filter *filter, int
 
 /* For single-byte encodings which use a conversion table */
 #define DEF_SB_TBL(id, name, mime_name, aliases, tbl_min, tbl) \
-	static int mbfl_filt_conv_##id##_wchar(int c, mbfl_convert_filter *filter) { \
-		return mbfl_conv_singlebyte_table(c, filter, tbl_min, tbl); \
-	} \
-	static int mbfl_filt_conv_wchar_##id(int c, mbfl_convert_filter *filter) { \
-		return mbfl_conv_reverselookup_table(c, filter, tbl_min, tbl); \
-	} \
 	static size_t mb_##id##_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state) \
 	{ \
 		unsigned char *p = *in, *e = p + *in_len; \
@@ -140,22 +83,6 @@ static int mbfl_conv_reverselookup_table(int c, mbfl_convert_filter *filter, int
 static const char *ascii_aliases[] = {"ANSI_X3.4-1968", "iso-ir-6", "ANSI_X3.4-1986", "ISO_646.irv:1991", "US-ASCII", "ISO646-US", "us", "IBM367", "IBM-367", "cp367", "csASCII", NULL};
 DEF_SB(ascii, "ASCII", "US-ASCII", ascii_aliases);
 
-static int mbfl_filt_conv_ascii_wchar(int c, mbfl_convert_filter *filter)
-{
-	CK((*filter->output_function)((c < 0x80) ? c : MBFL_BAD_INPUT, filter->data));
-	return 0;
-}
-
-static int mbfl_filt_conv_wchar_ascii(int c, mbfl_convert_filter *filter)
-{
-	if (c >= 0 && c < 0x80 && c != MBFL_BAD_INPUT) {
-		CK((*filter->output_function)(c, filter->data));
-	} else {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	}
-	return 0;
-}
-
 static size_t mb_ascii_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state)
 {
 	unsigned char *p = *in, *e = p + *in_len;
@@ -195,21 +122,6 @@ static void mb_wchar_to_ascii(uint32_t *in, size_t len, mb_convert_buf *buf, boo
 static const char *iso8859_1_aliases[] = {"ISO8859-1", "latin1", NULL};
 DEF_SB(8859_1, "ISO-8859-1", "ISO-8859-1", iso8859_1_aliases);
 
-static int mbfl_filt_conv_8859_1_wchar(int c, mbfl_convert_filter *filter)
-{
-	return (*filter->output_function)(c, filter->data);
-}
-
-static int mbfl_filt_conv_wchar_8859_1(int c, mbfl_convert_filter *filter)
-{
-	if (c >= 0 && c < 0x100 && c != MBFL_BAD_INPUT) {
-		CK((*filter->output_function)(c, filter->data));
-	} else {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	}
-	return 0;
-}
-
 static size_t mb_8859_1_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state)
 {
 	unsigned char *p = *in, *e = p + *in_len;
@@ -494,38 +406,6 @@ static const unsigned short cp1252_ucs_table[] = {
 };
 DEF_SB(cp1252, "Windows-1252", "Windows-1252", cp1252_aliases);
 
-static int mbfl_filt_conv_wchar_cp1252(int c, mbfl_convert_filter *filter)
-{
-	if (c < 0 || c == MBFL_BAD_INPUT) {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	} else if (c >= 0x100) {
-		for (int n = 0; n < 32; n++) {
-			if (c == cp1252_ucs_table[n]) {
-				CK((*filter->output_function)(0x80 + n, filter->data));
-				return 0;
-			}
-		}
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	} else if (c <= 0x7F || c >= 0xA0 || c == 0x81 || c == 0x8D || c == 0x8F || c == 0x90 || c == 0x9D) {
-		CK((*filter->output_function)(c, filter->data));
-	} else {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	}
-	return 0;
-}
-
-static int mbfl_filt_conv_cp1252_wchar(int c, mbfl_convert_filter *filter)
-{
-	int s;
-	if (c >= 0x80 && c < 0xA0) {
-		s = coalesce(cp1252_ucs_table[c - 0x80], MBFL_BAD_INPUT);
-	} else {
-		s = c;
-	}
-	CK((*filter->output_function)(s, filter->data));
-	return 0;
-}
-
 static size_t mb_cp1252_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state)
 {
 	unsigned char *p = *in, *e = p + *in_len;
@@ -701,32 +581,6 @@ static const unsigned char ucs_armscii8_table[] = {
 };
 DEF_SB(armscii8, "ArmSCII-8", "ArmSCII-8", armscii8_aliases);
 
-static int mbfl_filt_conv_armscii8_wchar(int c, mbfl_convert_filter *filter)
-{
-	CK((*filter->output_function)((c < 0xA0) ? c : coalesce(armscii8_ucs_table[c - 0xA0], MBFL_BAD_INPUT), filter->data));
-	return 0;
-}
-
-static int mbfl_filt_conv_wchar_armscii8(int c, mbfl_convert_filter *filter)
-{
-	if (c >= 0x28 && c <= 0x2F) {
-		CK((*filter->output_function)(ucs_armscii8_table[c - 0x28], filter->data));
-	} else if (c < 0 || c == MBFL_BAD_INPUT) {
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	} else if (c < 0xA0) {
-		CK((*filter->output_function)(c, filter->data));
-	} else {
-		for (int n = 0; n < 0x60; n++) {
-			if (c == armscii8_ucs_table[n]) {
-				CK((*filter->output_function)(0xA0 + n, filter->data));
-				return 0;
-			}
-		}
-		CK(mbfl_filt_conv_illegal_output(c, filter));
-	}
-	return 0;
-}
-
 static size_t mb_armscii8_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf, size_t bufsize, unsigned int *state)
 {
 	unsigned char *p = *in, *e = p + *in_len;