jonyoder opened a new pull request, #3293:
URL: https://github.com/apache/fory/pull/3293
## What does this PR do?
Fixes a panic in `readUTF16LE` when the byte count is odd (malformed UTF-16
data).
## Problem
When `readUTF16LE` receives an odd byte count, the function panics with:
```
panic: runtime error: index out of range [N] with length N
```
This occurs because the loop iterates up to `byteCount` but tries to access
`data[i+1]` on the last iteration when `i = byteCount - 1` (for odd
`byteCount`).
### Steps to Reproduce
```go
func TestReadUTF16LE_OddByteCount(t *testing.T) {
// Data: 5 bytes where only first 4 form valid UTF-16
data := []byte{0x48, 0x00, 0x69, 0x00, 0xFF}
buf := NewByteBuffer(data)
err := &Error{}
// This panics without the fix
result := readUTF16LE(buf, 5, err)
}
```
### Root Cause
In `go/fory/string.go`, line 89-90:
```go
for i := 0; i < byteCount; i += 2 {
u16s[i/2] = uint16(data[i]) | uint16(data[i+1])<<8 // Panics when i+1
>= len(data)
}
```
## Solution
Round down `byteCount` to the nearest even boundary before iterating:
```go
evenByteCount := byteCount &^ 1 // Round down to even
for i := 0; i < evenByteCount; i += 2 {
u16s[i/2] = uint16(data[i]) | uint16(data[i+1])<<8
}
```
This gracefully handles malformed UTF-16 data by ignoring the trailing byte
instead of panicking.
## Tests Added
- `TestReadUTF16LE_OddByteCount`: Verifies no panic with odd byte count
- `TestReadUTF16LE_SingleByte`: Verifies empty string for single byte input
- `TestReadUTF16LE_EvenByteCount`: Verifies normal case still works
- `TestReadUTF16LE_EmptyBuffer`: Verifies empty input handling
- `TestReadUTF16LE_SurrogatePair`: Verifies emoji/surrogate pair decoding
## Checklist
- [x] I have read the [Contributing
Guidelines](https://github.com/apache/fory/blob/main/CONTRIBUTING.md)
- [x] All tests pass (`go test -v ./...` in `go/fory`)
- [x] License headers are correct (hawkeye check passed)
- [x] PR title follows conventional commits format
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