diff options
Diffstat (limited to 'flatcc/src/runtime/emitter.c')
| -rw-r--r-- | flatcc/src/runtime/emitter.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/flatcc/src/runtime/emitter.c b/flatcc/src/runtime/emitter.c new file mode 100644 index 0000000..089ea00 --- /dev/null +++ b/flatcc/src/runtime/emitter.c @@ -0,0 +1,269 @@ +#include <stdlib.h> + +#include "flatcc/flatcc_rtconfig.h" +#include "flatcc/flatcc_emitter.h" + +static int advance_front(flatcc_emitter_t *E) +{ + flatcc_emitter_page_t *p = 0; + + if (E->front && E->front->prev != E->back) { + E->front->prev->page_offset = E->front->page_offset - FLATCC_EMITTER_PAGE_SIZE; + E->front = E->front->prev; + goto done; + } + if (!(p = FLATCC_EMITTER_ALLOC(sizeof(flatcc_emitter_page_t)))) { + return -1; + } + E->capacity += FLATCC_EMITTER_PAGE_SIZE; + if (E->front) { + p->prev = E->back; + p->next = E->front; + E->front->prev = p; + E->back->next = p; + E->front = p; + goto done; + } + /* + * The first page is shared between front and back to avoid + * double unecessary extra allocation. + */ + E->front = p; + E->back = p; + p->next = p; + p->prev = p; + E->front_cursor = E->front->page + FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_cursor = E->front_cursor; + E->front_left = FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_left = FLATCC_EMITTER_PAGE_SIZE - E->front_left; + p->page_offset = -(flatbuffers_soffset_t)E->front_left; + return 0; +done: + E->front_cursor = E->front->page + FLATCC_EMITTER_PAGE_SIZE; + E->front_left = FLATCC_EMITTER_PAGE_SIZE; + E->front->page_offset = E->front->next->page_offset - FLATCC_EMITTER_PAGE_SIZE; + return 0; +} + +static int advance_back(flatcc_emitter_t *E) +{ + flatcc_emitter_page_t *p = 0; + + if (E->back && E->back->next != E->front) { + E->back = E->back->next; + goto done; + } + if (!(p = FLATCC_EMITTER_ALLOC(sizeof(flatcc_emitter_page_t)))) { + return -1; + } + E->capacity += FLATCC_EMITTER_PAGE_SIZE; + if (E->back) { + p->prev = E->back; + p->next = E->front; + E->front->prev = p; + E->back->next = p; + E->back = p; + goto done; + } + /* + * The first page is shared between front and back to avoid + * double unecessary extra allocation. + */ + E->front = p; + E->back = p; + p->next = p; + p->prev = p; + E->front_cursor = E->front->page + FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_cursor = E->front_cursor; + E->front_left = FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_left = FLATCC_EMITTER_PAGE_SIZE - E->front_left; + p->page_offset = -(flatbuffers_soffset_t)E->front_left; + return 0; +done: + E->back_cursor = E->back->page; + E->back_left = FLATCC_EMITTER_PAGE_SIZE; + E->back->page_offset = E->back->prev->page_offset + FLATCC_EMITTER_PAGE_SIZE; + return 0; +} + +static int copy_front(flatcc_emitter_t *E, uint8_t *data, size_t size) +{ + size_t k; + + data += size; + while (size) { + k = size; + if (k > E->front_left) { + k = E->front_left; + if (k == 0) { + if (advance_front(E)) { + return -1; + } + continue; + } + } + E->front_cursor -= k; + E->front_left -= k; + data -= k; + size -= k; + memcpy(E->front_cursor, data, k); + }; + return 0; +} + +static int copy_back(flatcc_emitter_t *E, uint8_t *data, size_t size) +{ + size_t k; + + while (size) { + k = size; + if (k > E->back_left) { + k = E->back_left; + if (k == 0) { + if (advance_back(E)) { + return -1; + } + continue; + } + } + memcpy(E->back_cursor, data, k); + size -= k; + data += k; + E->back_cursor += k; + E->back_left -= k; + } + return 0; +} + +int flatcc_emitter_recycle_page(flatcc_emitter_t *E, flatcc_emitter_page_t *p) +{ + if (p == E->front || p == E->back) { + return -1; + } + p->next->prev = p->prev; + p->prev->next = p->next; + p->prev = E->front->prev; + p->next = E->front; + p->prev->next = p; + p->next->prev = p; + return 0; +} + +void flatcc_emitter_reset(flatcc_emitter_t *E) +{ + flatcc_emitter_page_t *p = E->front; + + if (!E->front) { + return; + } + E->back = E->front; + E->front_cursor = E->front->page + FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_cursor = E->front_cursor; + E->front_left = FLATCC_EMITTER_PAGE_SIZE / 2; + E->back_left = FLATCC_EMITTER_PAGE_SIZE - FLATCC_EMITTER_PAGE_SIZE / 2; + E->front->page_offset = -(flatbuffers_soffset_t)E->front_left; + /* Heuristic to reduce peak allocation over time. */ + if (E->used_average == 0) { + E->used_average = E->used; + } + E->used_average = E->used_average * 3 / 4 + E->used / 4; + E->used = 0; + while (E->used_average * 2 < E->capacity && E->back->next != E->front) { + /* We deallocate the page after back since it is less likely to be hot in cache. */ + p = E->back->next; + E->back->next = p->next; + p->next->prev = E->back; + FLATCC_EMITTER_FREE(p); + E->capacity -= FLATCC_EMITTER_PAGE_SIZE; + } +} + +void flatcc_emitter_clear(flatcc_emitter_t *E) +{ + flatcc_emitter_page_t *p = E->front; + + if (!p) { + return; + } + p->prev->next = 0; + while (p->next) { + p = p->next; + FLATCC_EMITTER_FREE(p->prev); + } + FLATCC_EMITTER_FREE(p); + memset(E, 0, sizeof(*E)); +} + +int flatcc_emitter(void *emit_context, + const flatcc_iovec_t *iov, int iov_count, + flatbuffers_soffset_t offset, size_t len) +{ + flatcc_emitter_t *E = emit_context; + uint8_t *p; + + E->used += len; + if (offset < 0) { + if (len <= E->front_left) { + E->front_cursor -= len; + E->front_left -= len; + p = E->front_cursor; + goto copy; + } + iov += iov_count; + while (iov_count--) { + --iov; + if (copy_front(E, iov->iov_base, iov->iov_len)) { + return -1; + } + } + } else { + if (len <= E->back_left) { + p = E->back_cursor; + E->back_cursor += len; + E->back_left -= len; + goto copy; + } + while (iov_count--) { + if (copy_back(E, iov->iov_base, iov->iov_len)) { + return -1; + } + ++iov; + } + } + return 0; +copy: + while (iov_count--) { + memcpy(p, iov->iov_base, iov->iov_len); + p += iov->iov_len; + ++iov; + } + return 0; +} + +void *flatcc_emitter_copy_buffer(flatcc_emitter_t *E, void *buf, size_t size) +{ + flatcc_emitter_page_t *p; + size_t len; + + if (size < E->used) { + return 0; + } + if (!E->front) { + return 0; + } + if (E->front == E->back) { + memcpy(buf, E->front_cursor, E->used); + return buf; + } + len = FLATCC_EMITTER_PAGE_SIZE - E->front_left; + memcpy(buf, E->front_cursor, len); + buf = (uint8_t *)buf + len; + p = E->front->next; + while (p != E->back) { + memcpy(buf, p->page, FLATCC_EMITTER_PAGE_SIZE); + buf = (uint8_t *)buf + FLATCC_EMITTER_PAGE_SIZE; + p = p->next; + } + memcpy(buf, p->page, FLATCC_EMITTER_PAGE_SIZE - E->back_left); + return buf; +} |