diff options
Diffstat (limited to '')
| -rw-r--r-- | src/backend/access/transam/xlogreader.c | 46 |
1 files changed, 37 insertions, 9 deletions
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c index c15da9d..e7ad331 100644 --- a/src/backend/access/transam/xlogreader.c +++ b/src/backend/access/transam/xlogreader.c @@ -457,18 +457,37 @@ XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversi if (state->decode_buffer_tail >= state->decode_buffer_head) { /* Empty, or tail is to the right of head. */ - if (state->decode_buffer_tail + required_space <= - state->decode_buffer + state->decode_buffer_size) + if (required_space <= + state->decode_buffer_size - + (state->decode_buffer_tail - state->decode_buffer)) { - /* There is space between tail and end. */ + /*- + * There is space between tail and end. + * + * +-----+--------------------+-----+ + * | |////////////////////|here!| + * +-----+--------------------+-----+ + * ^ ^ + * | | + * h t + */ decoded = (DecodedXLogRecord *) state->decode_buffer_tail; decoded->oversized = false; return decoded; } - else if (state->decode_buffer + required_space < - state->decode_buffer_head) + else if (required_space < + state->decode_buffer_head - state->decode_buffer) { - /* There is space between start and head. */ + /*- + * There is space between start and head. + * + * +-----+--------------------+-----+ + * |here!|////////////////////| | + * +-----+--------------------+-----+ + * ^ ^ + * | | + * h t + */ decoded = (DecodedXLogRecord *) state->decode_buffer; decoded->oversized = false; return decoded; @@ -477,10 +496,19 @@ XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversi else { /* Tail is to the left of head. */ - if (state->decode_buffer_tail + required_space < - state->decode_buffer_head) + if (required_space < + state->decode_buffer_head - state->decode_buffer_tail) { - /* There is space between tail and head. */ + /*- + * There is space between tail and head. + * + * +-----+--------------------+-----+ + * |/////|here! |/////| + * +-----+--------------------+-----+ + * ^ ^ + * | | + * t h + */ decoded = (DecodedXLogRecord *) state->decode_buffer_tail; decoded->oversized = false; return decoded; |