Add util functions to write in little-endian

This will be helpful for writing HID values.

PR #5270 <https://github.com/Genymobile/scrcpy/pull/5270>

app/src/util/binary.h

@@ -13,6 +13,12 @@ sc_write16be(uint8_t *buf, uint16_t value) {
     buf[1] = value;
 }
 
+static inline void
+sc_write16le(uint8_t *buf, uint16_t value) {
+    buf[0] = value;
+    buf[1] = value >> 8;
+}
+
 static inline void
 sc_write32be(uint8_t *buf, uint32_t value) {
     buf[0] = value >> 24;
@@ -21,12 +27,26 @@ sc_write32be(uint8_t *buf, uint32_t value) {
     buf[3] = value;
 }
 
+static inline void
+sc_write32le(uint8_t *buf, uint32_t value) {
+    buf[0] = value;
+    buf[1] = value >> 8;
+    buf[2] = value >> 16;
+    buf[3] = value >> 24;
+}
+
 static inline void
 sc_write64be(uint8_t *buf, uint64_t value) {
     sc_write32be(buf, value >> 32);
     sc_write32be(&buf[4], (uint32_t) value);
 }
 
+static inline void
+sc_write64le(uint8_t *buf, uint64_t value) {
+    sc_write32le(buf, (uint32_t) value);
+    sc_write32le(&buf[4], value >> 32);
+}
+
 static inline uint16_t
 sc_read16be(const uint8_t *buf) {
     return (buf[0] << 8) | buf[1];

app/tests/test_binary.c

@@ -42,6 +42,44 @@ static void test_write64be(void) {
     assert(buf[7] == 0xEF);
 }
 
+static void test_write16le(void) {
+    uint16_t val = 0xABCD;
+    uint8_t buf[2];
+
+    sc_write16le(buf, val);
+
+    assert(buf[0] == 0xCD);
+    assert(buf[1] == 0xAB);
+}
+
+static void test_write32le(void) {
+    uint32_t val = 0xABCD1234;
+    uint8_t buf[4];
+
+    sc_write32le(buf, val);
+
+    assert(buf[0] == 0x34);
+    assert(buf[1] == 0x12);
+    assert(buf[2] == 0xCD);
+    assert(buf[3] == 0xAB);
+}
+
+static void test_write64le(void) {
+    uint64_t val = 0xABCD1234567890EF;
+    uint8_t buf[8];
+
+    sc_write64le(buf, val);
+
+    assert(buf[0] == 0xEF);
+    assert(buf[1] == 0x90);
+    assert(buf[2] == 0x78);
+    assert(buf[3] == 0x56);
+    assert(buf[4] == 0x34);
+    assert(buf[5] == 0x12);
+    assert(buf[6] == 0xCD);
+    assert(buf[7] == 0xAB);
+}
+
 static void test_read16be(void) {
     uint8_t buf[2] = {0xAB, 0xCD};
 
@@ -108,6 +146,10 @@ int main(int argc, char *argv[]) {
     test_read32be();
     test_read64be();
 
+    test_write16le();
+    test_write32le();
+    test_write64le();
+
     test_float_to_u16fp();
     test_float_to_i16fp();
     return 0;