Skip to content

string.c: take the single-byte path for a string of nothing but ASCII #7209

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
matz merged 3 commits into from
Aug 16, 2026
Merged

string.c: take the single-byte path for a string of nothing but ASCII #7209

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
23bb77d
string.c: fold the single-byte test in `mrb_str_char_len()`
takumin Aug 16, 2026
b9e6eb1
string.c: escape a single-byte string byte by byte
takumin Aug 16, 2026
21bd476
string.c: cut the last byte of a single-byte string in `String#chop!`
takumin Aug 16, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 18 additions & 22 deletions src/string.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -639,20 +639,17 @@ mrb_str_char_len(mrb_state *mrb, mrb_value str)
struct RString *s = mrb_str_ptr(str);
mrb_int byte_len = RSTR_LEN(s);

/* A byte-indexed string has one position per byte, which is what
/* A single-byte string has one position per byte, which is what
mrb_str_char_to_byte() and mrb_str_byte_to_char() already answer for it.
Asked here only where the string stands, the same string was measured as
UTF-8 and reported a length its own indexing did not agree with.

7BIT is deliberately not recorded on the way out: it says the bytes hold
nothing multi-byte, while this returns early because of how the string is
read. force_encoding() can take the byte reading away again, and an answer
recorded here would outlive the reason for it. */
if (RSTR_BINARY_P(s)) {
return byte_len;
}

if (RSTR_CODERANGE(s) == MRB_STR_CODERANGE_7BIT) {
Nothing is recorded on the way out. A string of nothing but ASCII carries
that already, and a byte-read one returns here because of how it is read
rather than because of what its bytes are: 7BIT would be a claim about
bytes nothing has looked at, and force_encoding() can take the byte
reading away again and leave the claim standing. */
if (RSTR_SINGLE_BYTE_P(s)) {
return byte_len;
}
else {
Expand Down Expand Up @@ -1936,10 +1933,14 @@ str_escape(mrb_state *mrb, mrb_value str, mrb_bool inspect)

p = RSTRING_PTR(str); pend = RSTRING_END(str);
#ifdef MRB_UTF8_STRING
/* `inspect` passes a whole character through unescaped so it stays readable.
A byte-indexed string holds no characters to keep readable, so it escapes
byte by byte, which is what `dump` on the same string already did. */
if (RSTR_BINARY_P(mrb_str_ptr(str))) inspect = FALSE;
/* `inspect` passes a whole character through unescaped so it stays readable,
which is why it reads the character at every byte. A single-byte string
has none spelled in more than one byte: a byte-read one holds no
characters at all, and one of nothing but ASCII holds only characters the
escaping below writes out the same way. Both escape byte by byte, which is
what `dump` on the same string already did, and neither reads a character
to do it. */
if (RSTR_SINGLE_BYTE_P(mrb_str_ptr(str))) inspect = FALSE;
#endif
for (;p < pend; p++) {
unsigned char c, cc;
Expand Down Expand Up @@ -2397,22 +2398,17 @@ mrb_str_chop_bang(mrb_state *mrb, mrb_value str)

str_modify_keep_cr(mrb, s);
if (RSTR_LEN(s) > 0) {
mrb_int len;
/* The last position of a single-byte string is its last byte. */
mrb_int len = RSTR_LEN(s) - 1;
#ifdef MRB_UTF8_STRING
if (RSTR_BINARY_P(s)) {
/* The last position of a byte-indexed string is its last byte. */
len = RSTR_LEN(s) - 1;
}
else {
if (!RSTR_SINGLE_BYTE_P(s)) {
/* The last character starts at the head of the one covering the last
byte, which is read backwards from there rather than by walking the
whole string. */
const char* t = RSTR_PTR(s);
const char* e = t + RSTR_LEN(s);
len = mrb_utf8_char_head(t, e-1, e) - t;
}
#else
len = RSTR_LEN(s) - 1;
#endif
if (RSTR_PTR(s)[len] == '\n') {
if (len > 0 &&
Expand Down
Loading