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Commit 3418c6c

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fix(core): Improve StreamString::readBytes() speed with large buffers
Using `StreamString` on large buffers causes large movements of memory data when reading which can cause the TWDT to trigger, heap fragmentation or crash due to allocation failures. `StreamString` is definitely slower than cbuf.h for large buffers. Explanation of the issue with a small MRE: ESP32Async/ESPAsyncWebServer#148 (comment) This issue was discovered in the OpenDTU project : tbnobody/OpenDTU#2535 
1 parent b333bf2 commit 3418c6c

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lines changed

2 files changed

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‎cores/esp32/StreamString.cpp

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Original file line numberDiff line numberDiff line change
@@ -53,6 +53,26 @@ int StreamString::read() {
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return -1;
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}
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size_t StreamString::readBytes(char *buffer, size_t buffLen) {
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if (!buffLen || !buffer) {
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return 0;
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}
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const uint32_t start = millis();
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size_t count = 0;
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do {
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if (this->length()) {
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const size_t available = min(buffLen - count, (size_t)this->length());
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memcpy(buffer + count, c_str(), available);
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remove(0, available);
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count += available;
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}
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if (count == buffLen || _timeout == 0) {
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return count;
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}
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} while (millis() - start < _timeout);
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return count;
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}
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int StreamString::peek() {
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if (length()) {
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char c = charAt(0);

‎cores/esp32/StreamString.h

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@@ -31,6 +31,7 @@ class StreamString : public Stream, public String {
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int available() override;
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int read() override;
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size_t readBytes(char *buffer, size_t count) override;
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int peek() override;
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void flush() override;
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};

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