How to Handle Files with a Byte-Order Mark (BOM) in Go?

Reading Files with a Byte-Order Mark (BOM) in Go

In Go, handling Unicode files with or without a byte-order mark (BOM) requires manual processing. While there isn't an established way within the core library, the common approach involves:

Using a Buffered Reader:

Java.io.BufferedReader can be utilized to read data from a file, including the first few bytes. Here's an example:

import (
    "bufio"
    "os"
    "log"
)

func main() {
    fd, err := os.Open("filename")
    if err != nil {
        log.Fatal(err)
    }
    defer fd.Close()
    br := bufio.NewReader(fd)
    r, _, err := br.ReadRune()
    if err != nil {
        log.Fatal(err)
    }
    if r != '\uFEFF' {
        br.UnreadRune()
    }
}

Directly Reading First Bytes:

If the io.Seeker interface is supported, the first three bytes can be read and checked. If a BOM isn't identified, the file pointer can be reset to the start.

import (
    "os"
    "log"
)

func main() {
    fd, err := os.Open("filename")
    if err != nil {
        log.Fatal(err)
    }
    defer fd.Close()
    var bom [3]byte
    _, err = fd.Read(bom[:])
    if err != nil {
        log.Fatal(err)
    }
    if bom[0] != 0xef || bom[1] != 0xbb || bom[2] != 0xbf {
        _, err = fd.Seek(0, 0)
        if err != nil {
            log.Fatal(err)
        }
    }
}

Note:

These approaches assume UTF-8 encoding. Handling different encodings adds additional complexities.

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