urlyy commented on code in PR #2492:
URL: https://github.com/apache/fory/pull/2492#discussion_r2286969438
##########
rust/fory-core/src/buffer.rs:
##########
@@ -88,31 +88,27 @@ impl Writer {
}
pub fn var_int32(&mut self, value: i32) {
- if value >> 7 == 0 {
- self.u8(value as u8);
- } else if value >> 14 == 0 {
- let u1 = (value & 0x7F) | 0x80;
- let u2 = value >> 7;
- self.u16(((u1 << 8) | u2) as u16);
- } else if value >> 21 == 0 {
- let u1 = (value & 0x7F) | 0x80;
- let u2 = (value >> 7) | 0x80;
- self.u16(((u1 << 8) | u2) as u16);
- self.u8((value >> 14) as u8);
- } else if value >> 28 == 0 {
- let u1 = (value & 0x7F) | 0x80;
- let u2 = (value >> 7) | 0x80;
- let u3 = (value >> 14) | 0x80;
- let u4 = (value >> 21) | 0x80;
- self.u32(((u1 << 24) | (u2 << 16) | (u3 << 8) | u4) as u32);
+ let mut v = value as u32;
+ let len = if v < (1 << 7) {
+ 1
+ } else if v < (1 << 14) {
+ 2
+ } else if v < (1 << 21) {
+ 3
+ } else if v < (1 << 28) {
+ 4
} else {
- let u1 = (value & 0x7F) | 0x80;
- let u2 = (value >> 7) | 0x80;
- let u3 = (value >> 14) | 0x80;
- let u4 = (value >> 21) | 0x80;
- self.u32(((u1 << 24) | (u2 << 16) | (u3 << 8) | u4) as u32);
- self.u8((value >> 28) as u8);
+ 5
+ };
+ let mut buf = [0u8; 5];
Review Comment:
I wasn’t aiming to improve readability. Since the previous implementation
had issues, I wrote a version that is logically correct but less efficient. The
issues with the previous implementation were: 1) it didn’t handle
`little-endian` correctly when calling `u16()` and `u32()`, and 2) it didn’t
mask the lower 7 bits using `0x7F`. I’ve now added a `unit test` and modified
the previously written-merge code. The old implementation couldn’t pass the
test, but the current version does.
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