diff options
Diffstat (limited to 'libnetdata/circular_buffer/circular_buffer.c')
-rw-r--r-- | libnetdata/circular_buffer/circular_buffer.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/libnetdata/circular_buffer/circular_buffer.c b/libnetdata/circular_buffer/circular_buffer.c new file mode 100644 index 00000000..7ffe6b8b --- /dev/null +++ b/libnetdata/circular_buffer/circular_buffer.c @@ -0,0 +1,113 @@ +#include "../libnetdata.h" + +struct circular_buffer *cbuffer_new(size_t initial, size_t max, size_t *statistics) { + struct circular_buffer *buf = mallocz(sizeof(struct circular_buffer)); + buf->size = initial; + buf->data = mallocz(initial); + buf->write = 0; + buf->read = 0; + buf->max_size = max; + buf->statistics = statistics; + + if(buf->statistics) + __atomic_add_fetch(buf->statistics, sizeof(struct circular_buffer) + buf->size, __ATOMIC_RELAXED); + + return buf; +} + +void cbuffer_free(struct circular_buffer *buf) { + if (unlikely(!buf)) + return; + + if(buf->statistics) + __atomic_sub_fetch(buf->statistics, sizeof(struct circular_buffer) + buf->size, __ATOMIC_RELAXED); + + 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 old_size = buf->size; + 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; + + if(buf->statistics) + __atomic_add_fetch(buf->statistics, new_size - old_size, __ATOMIC_RELAXED); + + return 0; +} + +size_t cbuffer_available_size_unsafe(struct circular_buffer *buf) { + size_t len = (buf->write >= buf->read) ? (buf->write - buf->read) : (buf->size - buf->read + buf->write); + return buf->max_size - len; +} + +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; +} + +void cbuffer_flush(struct circular_buffer*buf) { + buf->write = 0; + buf->read = 0; +}
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