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optimize dynamic length string reading

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This commit is contained in:
Robin Appelman 2019-03-03 00:24:03 +01:00
commit 8fdcd6b4c4
1 changed files with 25 additions and 12 deletions
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47
src/buffer.rs
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@ -294,7 +294,7 @@ where
let usable_bytes = if E::is_le() {
&bytes[0..read]
} else {
&bytes[8 - read..8]
&bytes[USIZE_SIZE - read..USIZE_SIZE]
};
data.extend_from_slice(usable_bytes);
byte_left -= read;
@ -340,26 +340,39 @@ where
/// [`ReadError::NotEnoughData`]: enum.ReadError.html#variant.NotEnoughData
/// [`ReadError::Utf8Error`]: enum.ReadError.html#variant.Utf8Error
pub fn read_string(&self, position: usize, byte_len: Option<usize>) -> Result<String> {
let bytes = match byte_len {
Some(len) => self.read_bytes(position, len)?,
None => {
let mut acc = vec![];
let mut pos = position;
loop {
let byte = self.read_int(pos, 8)?;
acc.push(byte);
if byte == 0 {
break;
}
pos += 8;
}
acc
}
};
let bytes = self.read_string_bytes(position, byte_len)?;
let raw_string = String::from_utf8(bytes)?;
Ok(raw_string.trim_end_matches(char::from(0)).to_owned())
}
fn read_string_bytes(&self, position: usize, byte_len: Option<usize>) -> Result<Vec<u8>> {
match byte_len {
Some(len) => return self.read_bytes(position, len),
None => {
let mut acc = Vec::with_capacity(25);
let mut pos = position;
loop {
let read = min((USIZE_SIZE - 1) * 8, self.bit_len - pos);
let raw_bytes = self.read_usize(pos, read)?;
let bytes: [u8; USIZE_SIZE] = if E::is_le() {
raw_bytes.to_le_bytes()
} else {
raw_bytes.to_be_bytes()
};
for i in 0..(USIZE_SIZE - 1) {
let byte = if E::is_le() { bytes[i] } else { bytes[1 + i] };
if byte == 0 {
return Ok(acc);
}
acc.push(byte);
}
pos += read;
}
}
};
}
/// Read a sequence of bits from the buffer as float
///
/// # Errors