diff options
| -rw-r--r-- | library/std/src/io/buffered/bufwriter.rs | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/library/std/src/io/buffered/bufwriter.rs b/library/std/src/io/buffered/bufwriter.rs index 5c5f4467ef9..ef2769d431f 100644 --- a/library/std/src/io/buffered/bufwriter.rs +++ b/library/std/src/io/buffered/bufwriter.rs @@ -366,9 +366,11 @@ impl<W: Write> BufWriter<W> { // exactly. Doing otherwise would mean flushing the buffer, then writing this // input to the inner writer, which in many cases would be a worse strategy. - // SAFETY: We just called `self.flush_buf()`, so `self.buf.len()` is 0, and - // we entered this else block because `buf.len() < self.buf.capacity()`. - // Therefore, `buf.len() <= self.buf.capacity() - self.buf.len()`. + // SAFETY: There was either enough spare capacity already, or there wasn't and we + // flushed the buffer to ensure that there is. In the latter case, we know that there + // is because flushing ensured that our entire buffer is spare capacity, and we entered + // this block because the input buffer length is less than that capacity. In either + // case, it's safe to write the input buffer to our buffer. unsafe { self.write_to_buffer_unchecked(buf); } @@ -406,9 +408,11 @@ impl<W: Write> BufWriter<W> { // exactly. Doing otherwise would mean flushing the buffer, then writing this // input to the inner writer, which in many cases would be a worse strategy. - // SAFETY: We just called `self.flush_buf()`, so `self.buf.len()` is 0, and - // we entered this else block because `buf.len() < self.buf.capacity()`. - // Therefore, `buf.len() <= self.buf.capacity() - self.buf.len()`. + // SAFETY: There was either enough spare capacity already, or there wasn't and we + // flushed the buffer to ensure that there is. In the latter case, we know that there + // is because flushing ensured that our entire buffer is spare capacity, and we entered + // this block because the input buffer length is less than that capacity. In either + // case, it's safe to write the input buffer to our buffer. unsafe { self.write_to_buffer_unchecked(buf); } |