diff options
| -rw-r--r-- | client/main.cpp | 27 | ||||
| -rw-r--r-- | proto/puzbusv1.c | 33 | ||||
| -rw-r--r-- | proto/puzbusv1.h | 23 |
3 files changed, 62 insertions, 21 deletions
diff --git a/client/main.cpp b/client/main.cpp index 30d7045..dcc965b 100644 --- a/client/main.cpp +++ b/client/main.cpp @@ -17,31 +17,44 @@ int send_message() { size_t size; if (!pb_write(&output, &packed, &size)) { printf("error writing!\n"); - return 1; + return EXIT_FAILURE; } fwrite(packed, sizeof(packed[0]), size, stdout); fflush(stdout); - return 0; + return EXIT_SUCCESS; } int read_message() { freopen(NULL, "rb", stdin); // allow binary on stdin struct pb_msg input; - char buf[8]; // extremely small buffer to test chunked message parsing + char buf[4]; // extremely small buffer to test chunked message parsing size_t bytes = 0; + while ((bytes = fread(buf, sizeof(buf[0]), sizeof(buf), stdin)) > 0) { - if (!pb_read(&input, buf, bytes)) continue; + int ret = pb_read(&input, buf, bytes); + + // header read error + if (ret < 0) { + printf("error reading!\n"); + return EXIT_FAILURE; + } + + // continue reading if more bytes needed... + if (ret > 0) continue; + // message read completely! printf("address: 0x%02x\n", input.addr); printf("data: \"%.*s\"\n", input.length, input.data); free(input.data); - return 0; + return EXIT_SUCCESS; } - return 1; + // if we reach this point, data was read but it did not contain a complete + // message, and is thus considered a failure + return EXIT_FAILURE; } int main() { @@ -49,6 +62,6 @@ int main() { if (!isatty(fileno(stdin))) return read_message(); printf("please pipe some data in or out to use this program\n"); - return 0; + return EXIT_SUCCESS; } 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) { diff --git a/proto/puzbusv1.h b/proto/puzbusv1.h index 814bc93..95130c9 100644 --- a/proto/puzbusv1.h +++ b/proto/puzbusv1.h @@ -24,13 +24,26 @@ struct pb_msg { * \param buf pointer to input stream data chunk * \param buf_sz size of \p buf * - * \returns boolean true if a message was completely read, false if more data - * is required + * \returns Integer representing amount of bytes required to finish message, or + * -1 if the message header could not be read. If this function returns 0, the + * message in \p target is complete. * - * \note target->data will automatically be allocated by this function, and - * must be `free()`d by the caller when finished + * \note target->data will automatically be allocated by this function, even if + * the message is not fully parsed. This variable must be `free()`d by the + * caller after each complete message to prevent memory leaks. */ -bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz); +int pb_read(struct pb_msg* target, char* buf, size_t buf_sz); + +/** + * \brief reset the remaining message data counter + * + * Calling this function has the effect of forcing \c pb_read() to parse the + * next buffer chunk as the start of a new message. This function may be called + * before reading a TCP frame's data to mitigate any synchronization issues + * arising from earlier corrupt or otherwise malformed messages. + */ +void pb_read_reset(); + /** * \brief Allocate and write a msgpack-formatted message to \p buf * |