bfile

bfile

A buffer pool file I/O library for Go.

The purpose of the library is to provide I/O mechanisms for copying data to and from a buffer in user space and maintain complete control over how and when it transfers pages.

This is an alternative to using mmap on large DBMS like files.

Install

go get github.com/tidwall/bfile

Usage

Use the NewPager function to create a new Pager, which includes three functions: ReadAt, WriteAt, and Flush. The Pager reading and writing works like an os.File, but with an automatically maintained pool of buffered pages.

// Open a file for read/write
f, err := os.OpenFile("bigfile.dat", os.O_RDWR, 0)

// Create a new Pager for accessing the data in opened file.
p := bfile.NewPager(f)

// Read some data at a specific offset.
data := make([]byte, 50)
n, err := p.ReadAt(data, 827364)

// Write some data at the same offset.
n, err := p.WriteAt([]byte("hello"), c)

// Flush unwritten data to the underlying os.File
err = p.Flush()

There's also a Stream object for sequentially reading and writing data, which includes the three functions: Read, Write, and Flush.

// Create a new Pager
p := bfile.NewPager(f)

// Create a Stream that is backed by the Pager starting at a specific offset
s := p.Stream(827364)

// Read 50 bytes data at the offset 827364.
data := make([]byte, 50)
n, err := s.Read(data)

// Write the string "hello" at 827414, which is after the previous read.
n, err := s.Write([]byte("hello"))

// Flush unwritten data to the underlying os.File
err = p.Flush()

The default page size is 4096 and the default size of all buffered pages will not exceed 8 MB. These defaults can be changed by using the NewPagerSize function.

All operations are thread-safe.

Contact

Josh Baker @tidwall

License

Source code is available under the MIT License.