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115 lines
3.0 KiB
C
115 lines
3.0 KiB
C
#ifndef SC_BYTEBUF_H
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#define SC_BYTEBUF_H
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#include "common.h"
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#include <stdbool.h>
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#include <stdint.h>
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struct sc_bytebuf {
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uint8_t *data;
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// The actual capacity is (allocated - 1) so that head == tail is
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// non-ambiguous
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size_t alloc_size;
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size_t head; // writter cursor
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size_t tail; // reader cursor
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// empty: tail == head
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// full: ((tail + 1) % alloc_size) == head
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};
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bool
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sc_bytebuf_init(struct sc_bytebuf *buf, size_t alloc_size);
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/**
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* Copy from the bytebuf to a user-provided array
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*
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* The caller must check that len <= sc_bytebuf_read_available() (it is an
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* error to attempt to read more bytes than available).
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*
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* This function is guaranteed not to write to buf->head.
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*/
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void
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sc_bytebuf_read(struct sc_bytebuf *buf, uint8_t *to, size_t len);
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/**
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* Drop len bytes from the buffer
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*
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* The caller must check that len <= sc_bytebuf_read_available() (it is an
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* error to attempt to skip more bytes than available).
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*
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* This function is guaranteed not to write to buf->head.
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*
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* It is equivalent to call sc_bytebuf_read() to some array and discard the
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* array (but this function is more efficient since there is no copy).
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*/
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void
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sc_bytebuf_skip(struct sc_bytebuf *buf, size_t len);
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/**
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* Copy the user-provided array to the bytebuf
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*
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* The caller must check that len <= sc_bytebuf_write_available() (it is an
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* error to write more bytes than the remaining available space).
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*
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* This function is guaranteed not to write to buf->tail.
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*/
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void
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sc_bytebuf_write(struct sc_bytebuf *buf, const uint8_t *from, size_t len);
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/**
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* Copy the user-provided array to the bytebuf, but do not advance the cursor
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*
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* The caller must check that len <= sc_bytebuf_write_available() (it is an
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* error to write more bytes than the remaining available space).
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*
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* After this function is called, the write must be committed with
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* sc_bytebuf_commit_write().
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*
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* The purpose of this mechanism is to acquire a lock only to commit the write,
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* but not to perform the actual copy.
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*
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* This function is guaranteed not to access buf->tail.
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*/
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void
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sc_bytebuf_prepare_write(struct sc_bytebuf *buf, const uint8_t *from,
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size_t len);
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/**
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* Commit a prepared write
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*/
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void
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sc_bytebuf_commit_write(struct sc_bytebuf *buf, size_t len);
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/**
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* Return the number of bytes which can be read
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*
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* It is an error to read more bytes than available.
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*/
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static inline size_t
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sc_bytebuf_can_read(struct sc_bytebuf *buf) {
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return (buf->alloc_size + buf->head - buf->tail) % buf->alloc_size;
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}
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/**
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* Return the number of bytes which can be written
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*
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* It is an error to write more bytes than available.
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*/
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static inline size_t
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sc_bytebuf_can_write(struct sc_bytebuf *buf) {
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return (buf->alloc_size + buf->tail - buf->head - 1) % buf->alloc_size;
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}
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/**
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* Return the actual capacity of the buffer (can_read() + can_write())
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*/
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static inline size_t
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sc_bytebuf_capacity(struct sc_bytebuf *buf) {
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return buf->alloc_size - 1;
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}
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void
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sc_bytebuf_destroy(struct sc_bytebuf *buf);
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#endif
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