mirror of
https://github.com/mikecarper/MeshCore.git
synced 2026-09-14 18:15:34 +00:00
agessaman
b7b3b4dcf1
Improve the mqttSubstituteTopic function to ensure that it reports overflow when the output buffer is full, preventing silent truncation of topics. Update related tests to verify the new behavior for literal overflow and exact fit scenarios, enhancing robustness and correctness of topic handling.
57 lines
1.9 KiB
C
57 lines
1.9 KiB
C
#pragma once
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#include <stddef.h>
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#include <string.h>
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// Expand the {iata} {device} {token} {type} placeholders in a custom MQTT topic
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// template. Factored out of MQTTBridge::substituteTopicTemplate so the (bounded)
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// string expansion can be unit-tested on the host; the bridge passes its cached
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// _iata / _device_id, the slot token, and the message-type string.
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//
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// Returns false on buffer overflow or an empty result. buf is always
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// NUL-terminated. A null value substitutes as empty; an unknown "{...}" token is
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// copied through verbatim.
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static inline bool mqttSubstituteTopic(const char* tmpl, const char* iata,
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const char* device, const char* token,
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const char* type_str, char* buf, size_t buf_size) {
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if (!buf || buf_size == 0) return false;
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if (!iata) iata = "";
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if (!device) device = "";
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if (!token) token = "";
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if (!type_str) type_str = "";
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size_t out = 0;
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const char* p = tmpl ? tmpl : "";
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while (*p && out < buf_size - 1) {
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const char* sub = NULL;
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size_t adv = 0;
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if (strncmp(p, "{iata}", 6) == 0) {
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sub = iata; adv = 6;
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} else if (strncmp(p, "{device}", 8) == 0) {
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sub = device; adv = 8;
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} else if (strncmp(p, "{token}", 7) == 0) {
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sub = token; adv = 7;
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} else if (strncmp(p, "{type}", 6) == 0) {
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sub = type_str; adv = 6;
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}
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if (sub) {
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size_t len = strlen(sub);
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if (out + len >= buf_size) {
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buf[out] = '\0'; // keep buf terminated even on the overflow path
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return false;
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}
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memcpy(buf + out, sub, len);
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out += len;
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p += adv;
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} else {
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buf[out++] = *p++;
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}
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}
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buf[out] = '\0';
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// The loop also stops when the output buffer is full. If input remains,
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// report overflow just as we do for an oversized placeholder substitution;
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// callers must never publish a silently truncated topic.
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if (*p) return false;
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return out > 0;
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}
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