cstr.c File Reference

Implementation of high-performance C string with SSO. More...

#include "cstr.h"
#include <assert.h>
#include <ctype.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

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Functions
cstr *	cstr_init (size_t initial_capacity)
	Create a new heap-allocated cstr with a given initial capacity.
cstr *	cstr_new (const char *input)
	Create a new cstr from a C string.
cstr *	cstr_new_len (const char *data, size_t length)
	Create a new cstr from a buffer of known length (no strlen needed).
void	cstr_drop (cstr *s)
	Release only the internal heap buffer of an embedded cstr (one created via cstr_init_inplace). Does NOT free the cstr struct itself.
void	cstr_free (cstr *s)
	Free a heap-allocated cstr and its storage. Safe to call with NULL.
void	cstr_debug (const cstr *s)
	Print debug information about a cstr to stderr.
bool	cstr_reserve (cstr *s, size_t capacity)
	Ensure at least capacity usable bytes are available (NUL extra).
void	cstr_shrink_to_fit (cstr *s)
	Shrink heap allocation to fit the current length (frees wasted memory).
bool	cstr_append_char (cstr *s, char c)
	Append a single character.
bool	cstr_remove (cstr *s, size_t index, size_t count)
	Remove count characters starting at index.
void	cstr_remove_char (cstr *s, char c)
	Remove a specific character from every position.
void	cstr_remove_substr (cstr *s, size_t start, size_t slen)
	Remove a run of substr_length bytes starting at start.
int	cstr_cmp (const cstr *s1, const cstr *s2)
	Lexicographic compare. NULL < non-NULL; two NULLs are equal.
cstr *	cstr_join (const cstr **strings, size_t count, const char *delim)
	Join an array of cstr pointers with a delimiter.

Detailed Description

Implementation of high-performance C string with SSO.

Optimisation notes:

SSO self-referential pointer On init/SSO-promote, data is set to &s->buf[0]. Every read of string bytes goes through one unconditional pointer dereference — no ternary, no branch. Only free/resize needs cstr_is_heap().

uint32_t fields Struct is 32 bytes on 64-bit. length and capacity fit in L1 cache together with one hot 16-byte SSO string.

Search — cstr_search_impl() Uses a Sunday/Horspool bad-character skip table for needle length > 8. For short needles (≤ 8 bytes) it uses a SWAR (SIMD-Within-A-Register) first-byte scan to skip directly to candidates, avoiding glibc memmem's dynamic dispatch and the dynamic linker overhead it sometimes carries. Both paths avoid touching more haystack memory than necessary.

replace_all Single forward scan with a fixed-size stack-local offset table to avoid heap allocation for the common case (< 64 matches).

Growth policy Exact doubling from the next power-of-two above the request, ensuring amortised O(1) appends with no fractional-factor rounding surprises.

Definition in file cstr.c.

Function Documentation

cstr_init()

cstr * cstr_init

(

size_t

initial_capacity

)

Create a new heap-allocated cstr with a given initial capacity.

Parameters

initial_capacity

Desired usable capacity (NUL not counted).

Returns

New cstr, or NULL on OOM.

Note

Caller must call cstr_free().

Definition at line 127 of file cstr.c.

References cstr_init_inplace(), and CSTR_SSO_CAP.

Referenced by cstr_join().

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cstr_new()

cstr * cstr_new

(

const char *

input

)

Create a new cstr from a C string.

Parameters

input

NUL-terminated source. Must not be NULL.

Returns

New cstr, or NULL on OOM.

Note

Caller must call cstr_free().

Definition at line 146 of file cstr.c.

References cstr_new_len().

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cstr_new_len()

cstr * cstr_new_len	(	const char *	data,
		size_t	length
	)

Create a new cstr from a buffer of known length (no strlen needed).

Parameters

data	Pointer to characters (need not be NUL-terminated).
length	Number of bytes to copy.

Returns

New cstr, or NULL on OOM.

Definition at line 151 of file cstr.c.

References cstr_init_inplace(), cstr::data, and cstr::length.

Referenced by cstr_join(), and cstr_new().

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cstr_reserve()

bool cstr_reserve	(	cstr *	s,
		size_t	capacity
	)

Ensure at least capacity usable bytes are available (NUL extra).

Returns

true on success, false on OOM or overflow.

Definition at line 205 of file cstr.c.

Referenced by cstr_resize().

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