Initial files. Read rows from file is added.

Author: cinar

LICENSE.md

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+Copyright © 2021 Onur Cinar
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+[![GoDoc](https://godoc.org/github.com/cinar/csv2?status.svg)](https://godoc.org/github.com/cinar/csv2)
+[![License](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
+[![Build Status](https://travis-ci.com/cinar/csv2.svg?branch=master)](https://travis-ci.com/cinar/csv2)
+
+# Csv2 Go
+
+Csv2 is a lightweight Golang module for reading CSV files as individual rows or as a table.
+
+## Usage
+
+Install package.
+
+```bash
+go get github.com/cinar/csv2
+```
+
+Import Csv2.
+
+```Golang
+import (
+    "github.com/cinar/csv2"
+)
+```
+
+### Reading as individual rows
+
+Given that the CSV file contains the following columns.
+
+```CSV
+date,close,high,low,open,volume,adjClose,adjHigh,adjLow,adjOpen,adjVolume,divCash,splitFactor
+2015-09-18 00:00:00+00:00,43.48,43.99,43.33,43.5,63143684,39.5167038561,39.9802162518,39.3803766809,39.534880812800004,63143684,0.0,1.0
+```
+
+Define a structure for each individual row.
+
+```Golang
+// Daily price structure for each row.
+type dailyPrice struct {
+	Date        time.Time `format:"2006-01-02 15:04:05-07:00"`
+	Close       float64
+	High        float64
+	Low         float64
+	Open        float64
+	Volume      int64
+	AdjClose    float64
+	AdjHigh     float64
+	AdjLow      float64
+	AdjOpen     float64
+	AdjVolume   int64
+	DivCash     float64
+	SplitFactor float64
+}
+```
+
+Csv2 allows you to associate additional information about the colums through the tags. The following additional information is currently supported.
+
+Tag | Description | Example
+--- | --- | ---
+header | Column header for the field. | `header:"Date"`
+format | Date format for parsing. | `format:"2006-01-02 15:04:05-07:00"`
+
+Define an instance of a slice of row structure.
+
+```Golang
+var prices []dailyPrice
+```
+
+Use the [ReadRowsFromFile](https://pkg.go.dev/github.com/cinar/csv2#ReadRowsFromFile) function to read the CSV file into the slice.
+
+```Golang
+err := ReadRowsFromFile(testFile, true, &prices)
+if err != nil {
+    return err
+}
+```
+## License
+
+The source code is provided under MIT License.

csv2.go

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+package csv2
+
+import (
+	"encoding/csv"
+	"errors"
+	"fmt"
+	"io"
+	"math/bits"
+	"os"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const (
+	// Header name
+	TagHeader = "header"
+
+	// Format name
+	TagFormat = "format"
+)
+
+const (
+	timeFormat = "2006-01-02 15:04:05"
+)
+
+type columnInfo struct {
+	Header      string
+	ColumnIndex int
+	FieldIndex  int
+	Format      string
+}
+
+func setBoolFieldValue(fieldValue reflect.Value, stringValue string) error {
+	value, err := strconv.ParseBool(stringValue)
+	if err == nil {
+		fieldValue.SetBool(value)
+	}
+
+	return err
+}
+
+func setIntFieldValue(fieldValue reflect.Value, stringValue string, bitSize int) error {
+	value, err := strconv.ParseInt(stringValue, 10, bitSize)
+	if err == nil {
+		fieldValue.SetInt(value)
+	}
+
+	return err
+}
+
+func setUintFieldValue(fieldValue reflect.Value, stringValue string, bitSize int) error {
+	value, err := strconv.ParseUint(stringValue, 10, bitSize)
+	if err == nil {
+		fieldValue.SetUint(value)
+	}
+
+	return err
+}
+
+func setFloatFieldValue(fieldValue reflect.Value, stringValue string, bitSize int) error {
+	value, err := strconv.ParseFloat(stringValue, bitSize)
+	if err == nil {
+		fieldValue.SetFloat(value)
+	}
+
+	return err
+}
+
+func setTimeFieldValue(fieldValue reflect.Value, stringValue string, format string) error {
+	value, err := time.Parse(format, stringValue)
+	if err == nil {
+		fieldValue.Set(reflect.ValueOf(value))
+	}
+
+	return err
+}
+
+func setFieldValue(fieldValue reflect.Value, stringValue string, format string) error {
+	fieldKind := fieldValue.Kind()
+
+	switch fieldKind {
+	case reflect.String:
+		fieldValue.SetString(stringValue)
+		return nil
+
+	case reflect.Bool:
+		return setBoolFieldValue(fieldValue, stringValue)
+
+	case reflect.Int:
+		return setIntFieldValue(fieldValue, stringValue, bits.UintSize)
+
+	case reflect.Int8:
+		return setIntFieldValue(fieldValue, stringValue, 8)
+
+	case reflect.Int16:
+		return setIntFieldValue(fieldValue, stringValue, 16)
+
+	case reflect.Int32:
+		return setIntFieldValue(fieldValue, stringValue, 32)
+
+	case reflect.Int64:
+		return setIntFieldValue(fieldValue, stringValue, 64)
+
+	case reflect.Uint:
+		return setUintFieldValue(fieldValue, stringValue, bits.UintSize)
+
+	case reflect.Uint8:
+		return setUintFieldValue(fieldValue, stringValue, 8)
+
+	case reflect.Uint16:
+		return setUintFieldValue(fieldValue, stringValue, 16)
+
+	case reflect.Uint32:
+		return setUintFieldValue(fieldValue, stringValue, 32)
+
+	case reflect.Uint64:
+		return setUintFieldValue(fieldValue, stringValue, 64)
+
+	case reflect.Float32:
+		return setFloatFieldValue(fieldValue, stringValue, 32)
+
+	case reflect.Float64:
+		return setFloatFieldValue(fieldValue, stringValue, 64)
+
+	case reflect.Struct:
+		fieldTypeString := fieldValue.Type().String()
+
+		switch fieldTypeString {
+		case "time.Time":
+			return setTimeFieldValue(fieldValue, stringValue, format)
+
+		default:
+			return fmt.Errorf("unsupported struct type %s", fieldTypeString)
+		}
+
+	default:
+		return fmt.Errorf("unsupported field kind %s", fieldKind)
+	}
+}
+
+func getStructFieldsAsColumns(structType reflect.Type) []columnInfo {
+	columns := make([]columnInfo, structType.NumField())
+	for i := 0; i < structType.NumField(); i++ {
+		field := structType.Field(i)
+
+		header, ok := field.Tag.Lookup(TagHeader)
+		if !ok {
+			header = field.Name
+		}
+
+		format, ok := field.Tag.Lookup(TagFormat)
+		if !ok {
+			format = timeFormat
+		}
+
+		columns[i] = columnInfo{
+			Header:      header,
+			ColumnIndex: i,
+			FieldIndex:  i,
+			Format:      format,
+		}
+	}
+
+	return columns
+}
+
+func readHeader(csvReader csv.Reader, columns []columnInfo) error {
+	headers, err := csvReader.Read()
+	if err != nil {
+		return err
+	}
+
+	for _, column := range columns {
+		for i, header := range headers {
+			if strings.EqualFold(column.Header, header) {
+				column.ColumnIndex = i
+				break
+			}
+		}
+	}
+
+	return nil
+}
+
+// Read rows from reader.
+func ReadRowsFromReader(reader io.Reader, hasHeader bool, rows interface{}) error {
+	rowsPtrType := reflect.TypeOf(rows)
+	if rowsPtrType.Kind() != reflect.Ptr {
+		return errors.New("rows not a pointer")
+	}
+
+	rowsSliceType := rowsPtrType.Elem()
+	if rowsSliceType.Kind() != reflect.Slice {
+		return errors.New("rows not a pointer to slice")
+	}
+
+	rowType := rowsSliceType.Elem()
+	if rowType.Kind() != reflect.Struct {
+		return errors.New("rows not a pointer to slice of struct")
+	}
+
+	rowsPtr := reflect.ValueOf(rows)
+	rowsSlice := rowsPtr.Elem()
+
+	columns := getStructFieldsAsColumns(rowType)
+
+	csvReader := csv.NewReader(reader)
+
+	if hasHeader {
+		if err := readHeader(*csvReader, columns); err != nil {
+			return err
+		}
+	}
+
+	for {
+		record, err := csvReader.Read()
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			return err
+		}
+
+		row := reflect.New(rowType).Elem()
+
+		for _, column := range columns {
+			if err = setFieldValue(row.Field(column.FieldIndex), record[column.ColumnIndex], column.Format); err != nil {
+				return err
+			}
+		}
+
+		rowsSlice = reflect.Append(rowsSlice, row)
+	}
+
+	rowsPtr.Elem().Set(rowsSlice)
+
+	return nil
+}
+
+// Read rows from file.
+func ReadRowsFromFile(fileName string, hasHeader bool, rows interface{}) error {
+	file, err := os.Open(fileName)
+	if err != nil {
+		return err
+	}
+
+	defer file.Close()
+
+	return ReadRowsFromReader(file, hasHeader, rows)
+}