Writer#

A bounded append buffer that keeps counting after it runs out of room, so the same code can measure a message and then write it into a buffer of exactly the right size.

lwhttp_buffer_t b;
lwhttp_buffer_init(&b, NULL, 0);
lwhttp_write_header(&b, "Accept", "*/*");
lwhttp_write_end(&b);

char *out = malloc(b.len);
lwhttp_buffer_init(&b, out, b.len);
lwhttp_write_header(&b, "Accept", "*/*");
lwhttp_write_end(&b);
struct lwhttp_buffer_t#

Append-only output buffer that counts overflow instead of failing.

Appends that do not fit are not written but still advance lwhttp_buffer_t.len, so a pass with a NULL/0-sized buffer measures the size needed, and lwhttp_buffer_ok() tells whether everything fit. The buffer is never NUL-terminated.

char *data#

Output storage; may be NULL when lwhttp_buffer_t.size is 0.

size_t size#

Capacity of lwhttp_buffer_t.data in bytes.

size_t len#

Total bytes appended so far, including any that did not fit.

void lwhttp_buffer_init(lwhttp_buffer_t *buffer, char *data, size_t size)#

Initialise an empty output buffer.

Parameters:

  • buffer – Buffer to initialise.

  • data – Output storage, or NULL with size 0 to only measure.

  • size – Capacity of data in bytes.

void lwhttp_buffer_append(lwhttp_buffer_t *buffer, const void *data, size_t len)#

Append bytes. If they do not fit nothing is written, but the length still grows.

Parameters:

  • buffer – The buffer.

  • data – Bytes to append.

  • len – Number of bytes.

void lwhttp_buffer_append_str(lwhttp_buffer_t *buffer, const char *s)#

Append a NUL-terminated string without its terminator.

Parameters:

  • buffer – The buffer.

  • s – String to append; must not be NULL.

void lwhttp_buffer_append_u32(lwhttp_buffer_t *buffer, uint32_t value)#

Append an unsigned decimal number without leading zeros.

Parameters:

  • buffer – The buffer.

  • value – Number to append.

bool lwhttp_buffer_ok(const lwhttp_buffer_t *buffer)#

Check whether everything appended so far fit.

Parameters:

  • buffer – The buffer.

Returns:

true if lwhttp_buffer_t.len does not exceed lwhttp_buffer_t.size.

bool lwhttp_write_header(lwhttp_buffer_t *buffer, const char *name, const char *value)#

Append a validated Name: value line followed by CRLF.

Validation protects against header injection; capacity is not checked here, use lwhttp_buffer_ok().

Parameters:

  • buffer – The buffer.

  • name – Field name; must be a token (see lwhttp_is_token()).

  • value – Field value; must not contain control characters other than horizontal tab.

Returns:

true if the field was appended; false, with nothing appended, if name or value is invalid or NULL.

void lwhttp_write_end(lwhttp_buffer_t *buffer)#

Append the empty line (CRLF) that ends a header section.

Parameters:

  • buffer – The buffer.