path: root/common/test_utils.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// go-ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package common

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
)

// LoadJSON reads the given file and unmarshals its content.
func LoadJSON(file string, val interface{}) error {
    content, err := ioutil.ReadFile(file)
    if err != nil {
        return err
    }
    if err := json.Unmarshal(content, val); err != nil {
        if syntaxerr, ok := err.(*json.SyntaxError); ok {
            line := findLine(content, syntaxerr.Offset)
            return fmt.Errorf("JSON syntax error at %v:%v: %v", file, line, err)
        }
        return fmt.Errorf("JSON unmarshal error in %v: %v", file, err)
    }
    return nil
}

// findLine returns the line number for the given offset into data.
func findLine(data []byte, offset int64) (line int) {
    line = 1
    for i, r := range string(data) {
        if int64(i) >= offset {
            return
        }
        if r == '\n' {
            line++
        }
    }
    return
}