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qcow: Add ability to write a QcowHeader to a file

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For creating qcow files there needs to be the ability to save headers to
disk so they can be opened later.

Change-Id: Icf0134dd5ad3910c09f6e3766aca17ee003956c0
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/875115
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
This commit is contained in:
Dylan Reid 2018-01-18 11:08:48 -08:00 committed by chrome-bot
parent 9277879c51
commit 91fcad35c5
1 changed files with 40 additions and 1 deletions
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41
qcow/src/qcow.rs
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@ -25,6 +25,7 @@ pub enum Error {
NoRefcountClusters,
ReadingHeader(io::Error),
SizeTooSmallForNumberOfClusters,
WritingHeader(io::Error),
UnsupportedRefcountOrder,
UnsupportedVersion(u32),
}
@ -152,6 +153,39 @@ impl QcowHeader {
header_size: V3_BARE_HEADER_SIZE,
}
}
/// Write the header to `file`.
pub fn write_to<F: Write>(&self, file: &mut F) -> Result<()> {
// Writes the next u32 to the file.
fn write_u32_to_file<F: Write>(f: &mut F, value: u32) -> Result<()> {
f.write_u32::<BigEndian>(value).map_err(Error::WritingHeader)
}
// Writes the next u64 to the file.
fn write_u64_to_file<F: Write>(f: &mut F, value: u64) -> Result<()> {
f.write_u64::<BigEndian>(value).map_err(Error::WritingHeader)
}
write_u32_to_file(file, self.magic)?;
write_u32_to_file(file, self.version)?;
write_u64_to_file(file, self.backing_file_offset)?;
write_u32_to_file(file, self.backing_file_size)?;
write_u32_to_file(file, self.cluster_bits)?;
write_u64_to_file(file, self.size)?;
write_u32_to_file(file, self.crypt_method)?;
write_u32_to_file(file, self.l1_size)?;
write_u64_to_file(file, self.l1_table_offset)?;
write_u64_to_file(file, self.refcount_table_offset)?;
write_u32_to_file(file, self.refcount_table_clusters)?;
write_u32_to_file(file, self.nb_snapshots)?;
write_u64_to_file(file, self.snapshots_offset)?;
write_u64_to_file(file, self.incompatible_features)?;
write_u64_to_file(file, self.compatible_features)?;
write_u64_to_file(file, self.autoclear_features)?;
write_u32_to_file(file, self.refcount_order)?;
write_u32_to_file(file, self.header_size)?;
Ok(())
}
}
/// Represents a qcow2 file. This is a sparse file format maintained by the qemu project.
@ -556,7 +590,12 @@ mod tests {
#[test]
fn default_header() {
let _ = QcowHeader::create_for_size(0x10_0000);
let header = QcowHeader::create_for_size(0x10_0000);
let shm = SharedMemory::new(None).unwrap();
let mut disk_file: File = shm.into();
header.write_to(&mut disk_file).expect("Failed to write header to shm.");
disk_file.seek(SeekFrom::Start(0)).unwrap();
QcowFile::from(disk_file).expect("Failed to create Qcow from default Header");
}
#[test]