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#include "prism.h"
/******************************************************************************/
/* Character checks */
/******************************************************************************/
static inline bool
pm_char_is_hexadecimal_digits(const uint8_t *string, size_t length) {
for (size_t index = 0; index < length; index++) {
if (!pm_char_is_hexadecimal_digit(string[index])) {
return false;
}
}
return true;
}
// We don't call the char_width function unless we have to because it's
// expensive to go through the indirection of the function pointer. Instead we
// provide a fast path that will check if we can just return 1.
static inline size_t
pm_char_width(pm_parser_t *parser, const uint8_t *start, const uint8_t *end) {
if (parser->encoding_changed || (*start >= 0x80)) {
return parser->encoding.char_width(start, end - start);
} else {
return 1;
}
}
/******************************************************************************/
/* Lookup tables for characters */
/******************************************************************************/
// This is a lookup table for unescapes that only take up a single character.
static const uint8_t unescape_chars[] = {
['\''] = '\'',
['\\'] = '\\',
['a'] = '\a',
['b'] = '\b',
['e'] = '\033',
['f'] = '\f',
['n'] = '\n',
['r'] = '\r',
['s'] = ' ',
['t'] = '\t',
['v'] = '\v'
};
// This is a lookup table for whether or not an ASCII character is printable.
static const bool ascii_printable_chars[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0
};
static inline bool
char_is_ascii_printable(const uint8_t b) {
return (b < 0x80) && ascii_printable_chars[b];
}
/******************************************************************************/
/* Unescaping for segments */
/******************************************************************************/
// Scan the 1-3 digits of octal into the value. Returns the number of digits
// scanned.
static inline size_t
unescape_octal(const uint8_t *backslash, uint8_t *value, const uint8_t *end) {
*value = (uint8_t) (backslash[1] - '0');
if (backslash + 2 >= end || !pm_char_is_octal_digit(backslash[2])) {
return 2;
}
*value = (uint8_t) ((*value << 3) | (backslash[2] - '0'));
if (backslash + 3 >= end || !pm_char_is_octal_digit(backslash[3])) {
return 3;
}
*value = (uint8_t) ((*value << 3) | (backslash[3] - '0'));
return 4;
}
// Convert a hexadecimal digit into its equivalent value.
static inline uint8_t
unescape_hexadecimal_digit(const uint8_t value) {
return (uint8_t) ((value <= '9') ? (value - '0') : (value & 0x7) + 9);
}
// Scan the 1-2 digits of hexadecimal into the value. Returns the number of
// digits scanned.
static inline size_t
unescape_hexadecimal(const uint8_t *backslash, uint8_t *value, const uint8_t *end, pm_list_t *error_list) {
*value = 0;
if (backslash + 2 >= end || !pm_char_is_hexadecimal_digit(backslash[2])) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_HEXADECIMAL);
return 2;
}
*value = unescape_hexadecimal_digit(backslash[2]);
if (backslash + 3 >= end || !pm_char_is_hexadecimal_digit(backslash[3])) {
return 3;
}
*value = (uint8_t) ((*value << 4) | unescape_hexadecimal_digit(backslash[3]));
return 4;
}
// Scan the 4 digits of a Unicode escape into the value. Returns the number of
// digits scanned. This function assumes that the characters have already been
// validated.
static inline void
unescape_unicode(const uint8_t *string, size_t length, uint32_t *value) {
*value = 0;
for (size_t index = 0; index < length; index++) {
if (index != 0) *value <<= 4;
*value |= unescape_hexadecimal_digit(string[index]);
}
}
// Accepts the pointer to the string to write the unicode value along with the
// 32-bit value to write. Writes the UTF-8 representation of the value to the
// string and returns the number of bytes written.
static inline size_t
unescape_unicode_write(uint8_t *dest, uint32_t value, const uint8_t *start, const uint8_t *end, pm_list_t *error_list) {
if (value <= 0x7F) {
// 0xxxxxxx
dest[0] = (uint8_t) value;
return 1;
}
if (value <= 0x7FF) {
// 110xxxxx 10xxxxxx
dest[0] = (uint8_t) (0xC0 | (value >> 6));
dest[1] = (uint8_t) (0x80 | (value & 0x3F));
return 2;
}
if (value <= 0xFFFF) {
// 1110xxxx 10xxxxxx 10xxxxxx
dest[0] = (uint8_t) (0xE0 | (value >> 12));
dest[1] = (uint8_t) (0x80 | ((value >> 6) & 0x3F));
dest[2] = (uint8_t) (0x80 | (value & 0x3F));
return 3;
}
// At this point it must be a 4 digit UTF-8 representation. If it's not, then
// the input is invalid.
if (value <= 0x10FFFF) {
// 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
dest[0] = (uint8_t) (0xF0 | (value >> 18));
dest[1] = (uint8_t) (0x80 | ((value >> 12) & 0x3F));
dest[2] = (uint8_t) (0x80 | ((value >> 6) & 0x3F));
dest[3] = (uint8_t) (0x80 | (value & 0x3F));
return 4;
}
// If we get here, then the value is too big. This is an error, but we don't
// want to just crash, so instead we'll add an error to the error list and put
// in a replacement character instead.
if (error_list) pm_diagnostic_list_append(error_list, start, end, PM_ERR_ESCAPE_INVALID_UNICODE);
dest[0] = 0xEF;
dest[1] = 0xBF;
dest[2] = 0xBD;
return 3;
}
typedef enum {
PM_UNESCAPE_FLAG_NONE = 0,
PM_UNESCAPE_FLAG_CONTROL = 1,
PM_UNESCAPE_FLAG_META = 2,
PM_UNESCAPE_FLAG_EXPECT_SINGLE = 4
} pm_unescape_flag_t;
// Unescape a single character value based on the given flags.
static inline uint8_t
unescape_char(uint8_t value, const uint8_t flags) {
if (flags & PM_UNESCAPE_FLAG_CONTROL) {
value &= 0x1f;
}
if (flags & PM_UNESCAPE_FLAG_META) {
value |= 0x80;
}
return value;
}
// Read a specific escape sequence into the given destination.
static const uint8_t *
unescape(
pm_parser_t *parser,
uint8_t *dest,
size_t *dest_length,
const uint8_t *backslash,
const uint8_t *end,
const uint8_t flags,
pm_list_t *error_list
) {
switch (backslash[1]) {
case 'a':
case 'b':
case 'e':
case 'f':
case 'n':
case 'r':
case 's':
case 't':
case 'v':
if (dest) {
dest[(*dest_length)++] = unescape_char(unescape_chars[backslash[1]], flags);
}
return backslash + 2;
// \nnn octal bit pattern, where nnn is 1-3 octal digits ([0-7])
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9': {
uint8_t value;
const uint8_t *cursor = backslash + unescape_octal(backslash, &value, end);
if (dest) {
dest[(*dest_length)++] = unescape_char(value, flags);
}
return cursor;
}
// \xnn hexadecimal bit pattern, where nn is 1-2 hexadecimal digits ([0-9a-fA-F])
case 'x': {
uint8_t value;
const uint8_t *cursor = backslash + unescape_hexadecimal(backslash, &value, end, error_list);
if (dest) {
dest[(*dest_length)++] = unescape_char(value, flags);
}
return cursor;
}
// \u{nnnn ...} Unicode character(s), where each nnnn is 1-6 hexadecimal digits ([0-9a-fA-F])
// \unnnn Unicode character, where nnnn is exactly 4 hexadecimal digits ([0-9a-fA-F])
case 'u': {
if ((flags & PM_UNESCAPE_FLAG_CONTROL) | (flags & PM_UNESCAPE_FLAG_META)) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_UNICODE_CM_FLAGS);
return backslash + 2;
}
if ((backslash + 3) < end && backslash[2] == '{') {
const uint8_t *unicode_cursor = backslash + 3;
const uint8_t *extra_codepoints_start = NULL;
int codepoints_count = 0;
unicode_cursor += pm_strspn_whitespace(unicode_cursor, end - unicode_cursor);
while ((unicode_cursor < end) && (*unicode_cursor != '}')) {
const uint8_t *unicode_start = unicode_cursor;
size_t hexadecimal_length = pm_strspn_hexadecimal_digit(unicode_cursor, end - unicode_cursor);
// \u{nnnn} character literal allows only 1-6 hexadecimal digits
if (hexadecimal_length > 6) {
if (error_list) pm_diagnostic_list_append(error_list, unicode_cursor, unicode_cursor + hexadecimal_length, PM_ERR_ESCAPE_INVALID_UNICODE_LONG);
}
// there are not hexadecimal characters
else if (hexadecimal_length == 0) {
if (error_list) pm_diagnostic_list_append(error_list, unicode_cursor, unicode_cursor + hexadecimal_length, PM_ERR_ESCAPE_INVALID_UNICODE);
return unicode_cursor;
}
unicode_cursor += hexadecimal_length;
codepoints_count++;
if (flags & PM_UNESCAPE_FLAG_EXPECT_SINGLE && codepoints_count == 2)
extra_codepoints_start = unicode_start;
uint32_t value;
unescape_unicode(unicode_start, (size_t) (unicode_cursor - unicode_start), &value);
if (dest) {
*dest_length += unescape_unicode_write(dest + *dest_length, value, unicode_start, unicode_cursor, error_list);
}
unicode_cursor += pm_strspn_whitespace(unicode_cursor, end - unicode_cursor);
}
// ?\u{nnnn} character literal should contain only one codepoint and cannot be like ?\u{nnnn mmmm}
if (flags & PM_UNESCAPE_FLAG_EXPECT_SINGLE && codepoints_count > 1) {
if (error_list) pm_diagnostic_list_append(error_list, extra_codepoints_start, unicode_cursor - 1, PM_ERR_ESCAPE_INVALID_UNICODE_LITERAL);
}
if (unicode_cursor < end && *unicode_cursor == '}') {
unicode_cursor++;
} else {
if (error_list) pm_diagnostic_list_append(error_list, backslash, unicode_cursor, PM_ERR_ESCAPE_INVALID_UNICODE_TERM);
}
return unicode_cursor;
}
else if ((backslash + 5) < end && pm_char_is_hexadecimal_digits(backslash + 2, 4)) {
uint32_t value;
unescape_unicode(backslash + 2, 4, &value);
if (dest) {
*dest_length += unescape_unicode_write(dest + *dest_length, value, backslash + 2, backslash + 6, error_list);
}
return backslash + 6;
}
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_UNICODE);
return backslash + 2;
}
// \c\M-x meta control character, where x is an ASCII printable character
// \c? delete, ASCII 7Fh (DEL)
// \cx control character, where x is an ASCII printable character
case 'c':
if (backslash + 2 >= end) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL);
return end;
}
if (flags & PM_UNESCAPE_FLAG_CONTROL) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL_REPEAT);
return backslash + 2;
}
switch (backslash[2]) {
case '\\':
return unescape(parser, dest, dest_length, backslash + 2, end, flags | PM_UNESCAPE_FLAG_CONTROL, error_list);
case '?':
if (dest) {
dest[(*dest_length)++] = unescape_char(0x7f, flags);
}
return backslash + 3;
default: {
if (!char_is_ascii_printable(backslash[2])) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL);
return backslash + 2;
}
if (dest) {
dest[(*dest_length)++] = unescape_char(backslash[2], flags | PM_UNESCAPE_FLAG_CONTROL);
}
return backslash + 3;
}
}
// \C-x control character, where x is an ASCII printable character
// \C-? delete, ASCII 7Fh (DEL)
case 'C':
if (backslash + 3 >= end) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL);
return end;
}
if (flags & PM_UNESCAPE_FLAG_CONTROL) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL_REPEAT);
return backslash + 2;
}
if (backslash[2] != '-') {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_CONTROL);
return backslash + 2;
}
switch (backslash[3]) {
case '\\':
return unescape(parser, dest, dest_length, backslash + 3, end, flags | PM_UNESCAPE_FLAG_CONTROL, error_list);
case '?':
if (dest) {
dest[(*dest_length)++] = unescape_char(0x7f, flags);
}
return backslash + 4;
default:
if (!char_is_ascii_printable(backslash[3])) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_CONTROL);
return backslash + 2;
}
if (dest) {
dest[(*dest_length)++] = unescape_char(backslash[3], flags | PM_UNESCAPE_FLAG_CONTROL);
}
return backslash + 4;
}
// \M-\C-x meta control character, where x is an ASCII printable character
// \M-\cx meta control character, where x is an ASCII printable character
// \M-x meta character, where x is an ASCII printable character
case 'M': {
if (backslash + 3 >= end) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 1, PM_ERR_ESCAPE_INVALID_META);
return end;
}
if (flags & PM_UNESCAPE_FLAG_META) {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_META_REPEAT);
return backslash + 2;
}
if (backslash[2] != '-') {
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_META);
return backslash + 2;
}
if (backslash[3] == '\\') {
return unescape(parser, dest, dest_length, backslash + 3, end, flags | PM_UNESCAPE_FLAG_META, error_list);
}
if (char_is_ascii_printable(backslash[3])) {
if (dest) {
dest[(*dest_length)++] = unescape_char(backslash[3], flags | PM_UNESCAPE_FLAG_META);
}
return backslash + 4;
}
if (error_list) pm_diagnostic_list_append(error_list, backslash, backslash + 2, PM_ERR_ESCAPE_INVALID_META);
return backslash + 3;
}
// \n
case '\n':
return backslash + 2;
// \r
case '\r':
if (backslash + 2 < end && backslash[2] == '\n') {
return backslash + 3;
}
/* fallthrough */
// In this case we're escaping something that doesn't need escaping.
default: {
size_t width = pm_char_width(parser, backslash + 1, end);
if (dest) {
memcpy(dest + *dest_length, backslash + 1, width);
*dest_length += width;
}
return backslash + 1 + width;
}
}
}
/******************************************************************************/
/* Public functions and entrypoints */
/******************************************************************************/
// Unescape the contents of the given token into the given string using the
// given unescape mode. The supported escapes are:
//
// \a bell, ASCII 07h (BEL)
// \b backspace, ASCII 08h (BS)
// \t horizontal tab, ASCII 09h (TAB)
// \n newline (line feed), ASCII 0Ah (LF)
// \v vertical tab, ASCII 0Bh (VT)
// \f form feed, ASCII 0Ch (FF)
// \r carriage return, ASCII 0Dh (CR)
// \e escape, ASCII 1Bh (ESC)
// \s space, ASCII 20h (SPC)
// \\ backslash
// \nnn octal bit pattern, where nnn is 1-3 octal digits ([0-7])
// \xnn hexadecimal bit pattern, where nn is 1-2 hexadecimal digits ([0-9a-fA-F])
// \unnnn Unicode character, where nnnn is exactly 4 hexadecimal digits ([0-9a-fA-F])
// \u{nnnn ...} Unicode character(s), where each nnnn is 1-6 hexadecimal digits ([0-9a-fA-F])
// \cx or \C-x control character, where x is an ASCII printable character
// \M-x meta character, where x is an ASCII printable character
// \M-\C-x meta control character, where x is an ASCII printable character
// \M-\cx same as above
// \c\M-x same as above
// \c? or \C-? delete, ASCII 7Fh (DEL)
//
static void
pm_unescape_manipulate_string_or_char_literal(pm_parser_t *parser, pm_string_t *string, pm_unescape_type_t unescape_type, bool expect_single_codepoint) {
if (unescape_type == PM_UNESCAPE_NONE) {
// If we're not unescaping then we can reference the source directly.
return;
}
const uint8_t *backslash = pm_memchr(string->source, '\\', string->length, parser->encoding_changed, &parser->encoding);
if (backslash == NULL) {
// Here there are no escapes, so we can reference the source directly.
return;
}
// Here we have found an escape character, so we need to handle all escapes
// within the string.
uint8_t *allocated = malloc(string->length);
if (allocated == NULL) {
pm_diagnostic_list_append(&parser->error_list, string->source, string->source + string->length, PM_ERR_MALLOC_FAILED);
return;
}
// This is the memory address where we're putting the unescaped string.
uint8_t *dest = allocated;
size_t dest_length = 0;
// This is the current position in the source string that we're looking at.
// It's going to move along behind the backslash so that we can copy each
// segment of the string that doesn't contain an escape.
const uint8_t *cursor = string->source;
const uint8_t *end = string->source + string->length;
// For each escape found in the source string, we will handle it and update
// the moving cursor->backslash window.
while (backslash != NULL && backslash + 1 < end) {
assert(dest_length < string->length);
// This is the size of the segment of the string from the previous escape
// or the start of the string to the current escape.
size_t segment_size = (size_t) (backslash - cursor);
// Here we're going to copy everything up until the escape into the
// destination buffer.
memcpy(dest + dest_length, cursor, segment_size);
dest_length += segment_size;
switch (backslash[1]) {
case '\\':
case '\'':
dest[dest_length++] = unescape_chars[backslash[1]];
cursor = backslash + 2;
break;
default:
if (unescape_type == PM_UNESCAPE_WHITESPACE) {
if (backslash[1] == '\r' && backslash[2] == '\n') {
cursor = backslash + 2;
break;
}
if (pm_strspn_whitespace(backslash + 1, 1)) {
cursor = backslash + 1;
break;
}
}
if (unescape_type == PM_UNESCAPE_WHITESPACE || unescape_type == PM_UNESCAPE_MINIMAL) {
// In this case we're escaping something that doesn't need escaping.
dest[dest_length++] = '\\';
cursor = backslash + 1;
break;
}
// This is the only type of unescaping left. In this case we need to
// handle all of the different unescapes.
assert(unescape_type == PM_UNESCAPE_ALL);
uint8_t flags = PM_UNESCAPE_FLAG_NONE;
if (expect_single_codepoint) {
flags |= PM_UNESCAPE_FLAG_EXPECT_SINGLE;
}
cursor = unescape(parser, dest, &dest_length, backslash, end, flags, &parser->error_list);
break;
}
if (end > cursor) {
backslash = pm_memchr(cursor, '\\', (size_t) (end - cursor), parser->encoding_changed, &parser->encoding);
} else {
backslash = NULL;
}
}
// We need to copy the final segment of the string after the last escape.
if (end > cursor) {
memcpy(dest + dest_length, cursor, (size_t) (end - cursor));
} else {
cursor = end;
}
// If the string was already allocated, then we need to free that memory
// here. That's because we're about to override it with the escaped string.
pm_string_free(string);
// We also need to update the length at the end. This is because every escape
// reduces the length of the final string, and we don't want garbage at the
// end.
pm_string_owned_init(string, allocated, dest_length + ((size_t) (end - cursor)));
}
PRISM_EXPORTED_FUNCTION void
pm_unescape_manipulate_string(pm_parser_t *parser, pm_string_t *string, pm_unescape_type_t unescape_type) {
pm_unescape_manipulate_string_or_char_literal(parser, string, unescape_type, false);
}
void
pm_unescape_manipulate_char_literal(pm_parser_t *parser, pm_string_t *string, pm_unescape_type_t unescape_type) {
pm_unescape_manipulate_string_or_char_literal(parser, string, unescape_type, true);
}
// This function is similar to pm_unescape_manipulate_string, except it doesn't
// actually perform any string manipulations. Instead, it calculates how long
// the unescaped character is, and returns that value
size_t
pm_unescape_calculate_difference(pm_parser_t *parser, const uint8_t *backslash, pm_unescape_type_t unescape_type, bool expect_single_codepoint) {
assert(unescape_type != PM_UNESCAPE_NONE);
if (backslash + 1 >= parser->end) {
return 0;
}
switch (backslash[1]) {
case '\\':
case '\'':
return 2;
default: {
if (unescape_type == PM_UNESCAPE_WHITESPACE) {
if (backslash[1] == '\r' && backslash[2] == '\n') {
return 2;
}
size_t whitespace = pm_strspn_whitespace(backslash + 1, 1);
if (whitespace > 0) {
return whitespace;
}
}
if (unescape_type == PM_UNESCAPE_WHITESPACE || unescape_type == PM_UNESCAPE_MINIMAL) {
return 1 + pm_char_width(parser, backslash + 1, parser->end);
}
// This is the only type of unescaping left. In this case we need to
// handle all of the different unescapes.
assert(unescape_type == PM_UNESCAPE_ALL);
uint8_t flags = PM_UNESCAPE_FLAG_NONE;
if (expect_single_codepoint) {
flags |= PM_UNESCAPE_FLAG_EXPECT_SINGLE;
}
const uint8_t *cursor = unescape(parser, NULL, 0, backslash, parser->end, flags, NULL);
assert(cursor > backslash);
return (size_t) (cursor - backslash);
}
}
}
// This is one of the main entry points into the extension. It accepts a source
// string, a type of unescaping, and a pointer to a result string. It returns a
// boolean indicating whether or not the unescaping was successful.
PRISM_EXPORTED_FUNCTION bool
pm_unescape_string(const uint8_t *start, size_t length, pm_unescape_type_t unescape_type, pm_string_t *result) {
pm_parser_t parser;
pm_parser_init(&parser, start, length, NULL);
pm_string_shared_init(result, start, start + length);
pm_unescape_manipulate_string(&parser, result, unescape_type);
bool success = pm_list_empty_p(&parser.error_list);
pm_parser_free(&parser);
return success;
}
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