Viewing file:  circular_buffer.c (2.68 KB) -rw-r--r--
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#include "../libnetdata.h"
struct circular_buffer *cbuffer_new(size_t initial, size_t max) {
struct circular_buffer *result = mallocz(sizeof(*result));
result->size = initial;
result->data = mallocz(initial);
result->write = 0;
result->read = 0;
result->max_size = max;
return result;
}
void cbuffer_free(struct circular_buffer *buf) {
freez(buf->data);
freez(buf);
}
static int cbuffer_realloc_unsafe(struct circular_buffer *buf) {
// Check that we can grow
if (buf->size >= buf->max_size)
return 1;
size_t new_size = buf->size * 2;
if (new_size > buf->max_size)
new_size = buf->max_size;
// We know that: size < new_size <= max_size
// For simplicity align the current data at the bottom of the new buffer
char *new_data = mallocz(new_size);
if (buf->read == buf->write)
buf->write = 0; // buffer is empty
else if (buf->read < buf->write) {
memcpy(new_data, buf->data + buf->read, buf->write - buf->read);
buf->write -= buf->read;
} else {
size_t top_part = buf->size - buf->read;
memcpy(new_data, buf->data + buf->read, top_part);
memcpy(new_data + top_part, buf->data, buf->write);
buf->write = top_part + buf->write;
}
buf->read = 0;
// Switch buffers
freez(buf->data);
buf->data = new_data;
buf->size = new_size;
return 0;
}
int cbuffer_add_unsafe(struct circular_buffer *buf, const char *d, size_t d_len) {
size_t len = (buf->write >= buf->read) ? (buf->write - buf->read) : (buf->size - buf->read + buf->write);
while (d_len + len >= buf->size) {
if (cbuffer_realloc_unsafe(buf)) {
return 1;
}
}
// Guarantee: write + d_len cannot hit read
if (buf->write + d_len < buf->size) {
memcpy(buf->data + buf->write, d, d_len);
buf->write += d_len;
}
else {
size_t top_part = buf->size - buf->write;
memcpy(buf->data + buf->write, d, top_part);
memcpy(buf->data, d + top_part, d_len - top_part);
buf->write = d_len - top_part;
}
return 0;
}
// Assume caller does not remove too many bytes (i.e. read will jump over write)
void cbuffer_remove_unsafe(struct circular_buffer *buf, size_t num) {
buf->read += num;
// Assume num < size (i.e. caller cannot remove more bytes than are in the buffer)
if (buf->read >= buf->size)
buf->read -= buf->size;
}
size_t cbuffer_next_unsafe(struct circular_buffer *buf, char **start) {
if (start != NULL)
*start = buf->data + buf->read;
if (buf->read <= buf->write) {
return buf->write - buf->read; // Includes empty case
}
return buf->size - buf->read;
}
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