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Optimize reading in files

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This commit is contained in:
Josh Holmer 2020-10-22 09:51:25 -04:00
parent bd0c4061bd
commit b446a8a92e
1 changed files with 8 additions and 9 deletions
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17
src/png/mod.rs
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@ -10,7 +10,7 @@ use indexmap::IndexMap;
use rgb::ComponentSlice; use rgb::ComponentSlice;
use rgb::RGBA8; use rgb::RGBA8;
use std::fs::File; use std::fs::File;
use std::io::{Read, Seek, SeekFrom}; use std::io::{BufReader, Read};
use std::iter::Iterator; use std::iter::Iterator;
use std::path::Path; use std::path::Path;
use std::sync::Arc; use std::sync::Arc;
@ -62,25 +62,24 @@ impl PngData {
} }
pub fn read_file(filepath: &Path) -> Result<Vec<u8>, PngError> { pub fn read_file(filepath: &Path) -> Result<Vec<u8>, PngError> {
let mut file = match File::open(filepath) { let file = match File::open(filepath) {
Ok(f) => f, Ok(f) => f,
Err(_) => return Err(PngError::new("Failed to open file for reading")), Err(_) => return Err(PngError::new("Failed to open file for reading")),
}; };
let file_len = file.metadata().map(|m| m.len() as usize).unwrap_or(0);
let mut reader = BufReader::new(file);
// Check file for PNG header // Check file for PNG header
let mut header = [0; 8]; let mut header = [0; 8];
if file.read_exact(&mut header).is_err() { if reader.read_exact(&mut header).is_err() {
return Err(PngError::new("Not a PNG file: too small")); return Err(PngError::new("Not a PNG file: too small"));
} }
if !file_header_is_valid(&header) { if !file_header_is_valid(&header) {
return Err(PngError::new("Invalid PNG header detected")); return Err(PngError::new("Invalid PNG header detected"));
} }
if file.seek(SeekFrom::Start(0)).is_err() {
return Err(PngError::new("Failed to read from file"));
}
// Read raw png data into memory // Read raw png data into memory
let mut byte_data: Vec<u8> = let mut byte_data: Vec<u8> = Vec::with_capacity(file_len);
Vec::with_capacity(file.metadata().map(|m| m.len() as usize).unwrap_or(0)); byte_data.extend_from_slice(&header);
match file.read_to_end(&mut byte_data) { match reader.read_to_end(&mut byte_data) {
Ok(_) => (), Ok(_) => (),
Err(_) => return Err(PngError::new("Failed to read from file")), Err(_) => return Err(PngError::new("Failed to read from file")),
} }