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Fix binarySearch() convergence at page boundaries #159

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Fix binarySearch() convergence at page boundaries #159

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64eab21
Fix binarySearch() missing return statement (UB)
94xhn Jul 17, 2026
b2971cc
fix(search): guard binary page bounds
94xhn Jul 17, 2026
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7 changes: 4 additions & 3 deletions src/embedDB/embedDB.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1389,15 +1389,16 @@ int8_t binarySearch(embedDBState *state, void *buffer, void *key) {
if (readPage(state, pageId % state->numDataPages) != 0)
return -1;

if (first >= last)
break;

if (state->compareKey(key, embedDBGetMinKey(state, buffer)) < 0) {
/* Key is less than smallest record in block. */
if (pageId == first)
return -1;
last = pageId - 1;
pageId = (first + last) / 2;
} else if (state->compareKey(key, embedDBGetMaxKey(state, buffer)) > 0) {
/* Key is larger than largest record in block. */
if (pageId == last)
return -1;
first = pageId + 1;
pageId = (first + last) / 2;
} else {
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32 changes: 32 additions & 0 deletions test/test_embedDB/test_embedDB.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,16 @@

#include "unity.h"

extern "C" int8_t binarySearch(embedDBState *state, void *buffer, void *key);

embedDBState *state;
static int8_t (*originalFileRead)(void *, uint32_t, uint32_t, void *);
static uint32_t lastReadPage;

static int8_t trackFileRead(void *buffer, uint32_t pageNum, uint32_t pageSize, void *file) {
lastReadPage = pageNum;
return originalFileRead(buffer, pageNum, pageSize, file);
}

void setupEmbedDB() {
state = (embedDBState *)malloc(sizeof(embedDBState));
Expand Down Expand Up @@ -241,6 +250,28 @@ void embedDBFlush_does_not_write_when_nothing_in_buffer() {
TEST_ASSERT_EQUAL_UINT32_MESSAGE(1000, state->numAvailDataPages, "embedDBFlush should not change numAvailDataPages when no records in buffer.");
}

void binarySearch_stops_at_first_page_for_lower_key() {
for (uint32_t key = 10; key < 136; key++) {
uint32_t data = key;
TEST_ASSERT_EQUAL_INT8(0, embedDBPut(state, &key, &data));
}
TEST_ASSERT_EQUAL_INT8(0, embedDBFlush(state));
TEST_ASSERT_EQUAL_UINT32(2, state->nextDataPageId);

state->bufferedPageId = UINT32_MAX;
originalFileRead = state->fileInterface->read;
state->fileInterface->read = trackFileRead;
lastReadPage = UINT32_MAX;

uint32_t key = 9;
void *readBuffer = (int8_t *)state->buffer + state->pageSize;
int8_t result = binarySearch(state, readBuffer, &key);

state->fileInterface->read = originalFileRead;
TEST_ASSERT_EQUAL_INT8(-1, result);
TEST_ASSERT_EQUAL_UINT32(0, lastReadPage);
}

int runUnityTests(void) {
UNITY_BEGIN();
RUN_TEST(embedDB_initial_configuration_is_correct);
Expand All @@ -250,6 +281,7 @@ int runUnityTests(void) {
RUN_TEST(embedDB_put_inserts_one_more_than_one_page_of_records_correctly);
RUN_TEST(iteratorReturnsCorrectRecords);
RUN_TEST(embedDBFlush_does_not_write_when_nothing_in_buffer);
RUN_TEST(binarySearch_stops_at_first_page_for_lower_key);
return UNITY_END();
}

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