From 9ff66bfe22c5f378584db2a57160d00b585a77ce Mon Sep 17 00:00:00 2001 From: lonkaars Date: Mon, 20 May 2024 10:25:21 +0200 Subject: make puzbus slightly more robust --- proto/puzbusv1.c | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-) (limited to 'proto/puzbusv1.c') diff --git a/proto/puzbusv1.c b/proto/puzbusv1.c index d6cd597..3be4939 100644 --- a/proto/puzbusv1.c +++ b/proto/puzbusv1.c @@ -7,21 +7,32 @@ #include "puzbusv1.h" -bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz) { - // remaining bytes to be read to target->data; this is the only variable that - // needs to persist between buffer blocks, and is therefore static - static size_t rdata = 0; +/** + * \brief Remaining bytes to be read to target->data + * + * This is the only variable that needs to persist between buffer blocks. It is + * declared in the global scope to allow resetting using the \c pb_read_reset() + * function. + * + * \note \p rdata may be reset by calling \c pb_read_reset() + */ +static size_t rdata = 0; +int pb_read(struct pb_msg* target, char* buf, size_t buf_sz) { // a new reader is used per buffer block passed to this function mpack_reader_t reader; mpack_reader_init_data(&reader, buf, buf_sz); // at start of message if (rdata == 0) { - // NOTE: This approach will crash and burn when target->addr can be read - // and target->length is past the end of the current buffer block. This is - // a highly unlikely scenario, as pb_read is called for each chunk of a TCP - // frame, and frames (should) include only one puzzle bus message. + // NOTE: The entire start of a message needs to be readable from the buffer + // at this point. When target->addr can be read and target->length is past + // the end of the current buffer block, this function will crash and burn. + // This is a highly unlikely scenario, as pb_read is called for each chunk + // of a TCP frame, and frames (should) include only one puzzle bus message. + // The check here is kind of optional. + if (buf_sz < 4) return -1; + target->addr = mpack_expect_u16(&reader); target->length = rdata = mpack_expect_bin(&reader); target->data = (char*) malloc(target->length); @@ -35,7 +46,11 @@ bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz) { rdata -= to_read; // if rdata = 0, the message was completely read - return rdata == 0; + return rdata; +} + +void pb_read_reset() { + rdata = 0; } bool pb_write(struct pb_msg* target, char** buf, size_t* buf_sz) { -- cgit v1.2.3