lang.IndexTemplateTable() (template API)Returns element(s) from a table
This is a template API you can use for your custom data types.
It should only be called from ReadIndex() and ReadNotIndex() functions.
This function ensures consistency with the index, [, builtin when used with different Murex data types. Thus making indexing a data type agnostic capability.
Example calling lang.IndexTemplateTable() function:
package generic
import (
"bytes"
"strings"
"github.com/lmorg/murex/lang"
)
func index(p *lang.Process, params []string) error {
cRecords := make(chan []string, 1)
go func() {
err := p.Stdin.ReadLine(func(b []byte) {
cRecords <- rxWhitespace.Split(string(bytes.TrimSpace(b)), -1)
})
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
close(cRecords)
}()
marshaller := func(s []string) (b []byte) {
b = []byte(strings.Join(s, "\t"))
return
}
return lang.IndexTemplateTable(p, params, cRecords, marshaller)
}package lang
import (
"errors"
"fmt"
"regexp"
"strconv"
"strings"
"github.com/lmorg/murex/utils"
)
const (
byRowNumber = iota + 1
byColumnNumber
byColumnName
maxReportedUnmatched = 5
)
var (
rxColumnPrefixOld = regexp.MustCompile(`^:[0-9]+$`)
rxRowSuffixOld = regexp.MustCompile(`^[0-9]+:$`)
rxColumnPrefixNew = regexp.MustCompile(`^\*[a-zA-Z]$`)
rxRowSuffixNew = regexp.MustCompile(`^\*[0-9]+$`)
errMixAndMatch = errors.New("you cannot mix and match matching modes")
)
// IndexTemplateTable is a handy standard indexer you can use in your custom data types for tabulated / streamed data.
// The point of this is to minimize code rewriting and standardising the behavior of the indexer.
func IndexTemplateTable(p *Process, params []string, cRecords chan []string, marshaller func([]string) []byte) error {
if p.IsNot {
return ittNot(p, params, cRecords, marshaller)
}
return ittIndex(p, params, cRecords, marshaller)
}
func charToIndex(b byte) int {
if b > 96 {
return int(b - 97)
}
return int(b - 65)
}
func ittIndex(p *Process, params []string, cRecords chan []string, marshaller func([]string) []byte) (err error) {
var (
mode int
matchStr []string
matchInt []int
unmatched []string
unmatchedCount int
)
defer func() {
if len(unmatched) != 0 {
p.ExitNum = 1
if unmatchedCount > maxReportedUnmatched {
unmatched = append(unmatched, fmt.Sprintf("...plus %d more", unmatchedCount-maxReportedUnmatched))
}
err = fmt.Errorf("some records did not contain all of the requested fields:%s%s",
utils.NewLineString,
strings.Join(unmatched, utils.NewLineString))
}
}()
errUnmatched := func(recs []string) {
unmatchedCount++
if unmatchedCount > maxReportedUnmatched {
return
}
unmatched = append(unmatched, strings.Join(recs, "\t"))
}
for i := range params {
switch {
case rxRowSuffixOld.MatchString(params[i]):
if mode != 0 && mode != byRowNumber {
return errMixAndMatch
}
mode = byRowNumber
num, _ := strconv.Atoi(params[i][:len(params[i])-1])
matchInt = append(matchInt, num)
case rxRowSuffixNew.MatchString(params[i]):
if mode != 0 && mode != byRowNumber {
return errMixAndMatch
}
mode = byRowNumber
num, _ := strconv.Atoi(params[i][1:])
matchInt = append(matchInt, num-1) // Don't count from zero
case rxColumnPrefixOld.MatchString(params[i]):
if mode != 0 && mode != byColumnNumber {
return errMixAndMatch
}
mode = byColumnNumber
num, _ := strconv.Atoi(params[i][1:])
matchInt = append(matchInt, num)
case rxColumnPrefixNew.MatchString(params[i]):
if mode != 0 && mode != byColumnNumber {
return errMixAndMatch
}
mode = byColumnNumber
num := charToIndex(params[i][1])
matchInt = append(matchInt, num)
default:
if mode != 0 && mode != byColumnName {
return errMixAndMatch
}
matchStr = append(matchStr, params[i])
mode = byColumnName
}
}
switch mode {
case byRowNumber:
var (
ordered = true
last int
max int
)
// check order
for _, i := range matchInt {
if i < last {
ordered = false
}
if i > max {
max = i
}
last = i
}
if ordered {
// ordered matching - for this we can just read in the records we want sequentially. Low memory overhead
var i int
for {
recs, ok := <-cRecords
if !ok {
return nil
}
if i == matchInt[0] {
_, err = p.Stdout.Writeln(marshaller(recs))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
if len(matchInt) == 1 {
matchInt[0] = -1
return nil
}
matchInt = matchInt[1:]
}
i++
}
} else {
// unordered matching - for this we load the entire data set into memory - up until the maximum value
var (
i int
lines = make([][]string, max+1)
)
for {
recs, ok := <-cRecords
if !ok {
break
}
if i <= max {
lines[i] = recs
}
i++
}
for _, j := range matchInt {
_, err = p.Stdout.Writeln(marshaller(lines[j]))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
}
return nil
}
case byColumnNumber:
for {
recs, ok := <-cRecords
if !ok {
return nil
}
var line []string
for _, i := range matchInt {
if i < len(recs) {
line = append(line, recs[i])
} else {
if len(recs) == 0 || (len(recs) == 1 && recs[0] == "") {
continue
}
errUnmatched(recs)
}
}
if len(line) != 0 {
_, err = p.Stdout.Writeln(marshaller(line))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
}
}
case byColumnName:
var (
lineNum int
headings = make(map[string]int)
)
for {
var line []string
recs, ok := <-cRecords
if !ok {
return nil
}
if lineNum == 0 {
for i := range recs {
headings[recs[i]] = i + 1
}
for i := range matchStr {
if headings[matchStr[i]] != 0 {
line = append(line, matchStr[i])
}
}
if len(line) != 0 {
_, err = p.Stdout.Writeln(marshaller(line))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
}
} else {
for i := range matchStr {
col := headings[matchStr[i]]
if col != 0 && col < len(recs)+1 {
line = append(line, recs[col-1])
} else {
if len(recs) == 0 || (len(recs) == 1 && recs[0] == "") {
continue
}
errUnmatched(recs)
}
}
if len(line) != 0 {
_, err = p.Stdout.Writeln(marshaller(line))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
}
}
lineNum++
}
default:
return errors.New("you haven't selected any rows / columns")
}
}
func ittNot(p *Process, params []string, cRecords chan []string, marshaller func([]string) []byte) error {
var (
mode int
matchStr = make(map[string]bool)
matchInt = make(map[int]bool)
)
for i := range params {
switch {
case rxRowSuffixOld.MatchString(params[i]):
if mode != 0 && mode != byRowNumber {
return errMixAndMatch
}
mode = byRowNumber
num, _ := strconv.Atoi(params[i][:len(params[i])-1])
matchInt[num] = true
case rxRowSuffixNew.MatchString(params[i]):
if mode != 0 && mode != byRowNumber {
return errMixAndMatch
}
mode = byRowNumber
num, _ := strconv.Atoi(params[i][1:])
matchInt[num+1] = true // Don't count from zero
case rxColumnPrefixOld.MatchString(params[i]):
if mode != 0 && mode != byColumnNumber {
return errMixAndMatch
}
mode = byColumnNumber
num, _ := strconv.Atoi(params[i][1:])
matchInt[num] = true
case rxColumnPrefixNew.MatchString(params[i]):
if mode != 0 && mode != byColumnNumber {
return errMixAndMatch
}
mode = byColumnNumber
num := charToIndex(params[i][1])
matchInt[num] = true
default:
if mode != 0 && mode != byColumnName {
return errMixAndMatch
}
matchStr[params[i]] = true
mode = byColumnName
}
}
switch mode {
case byRowNumber:
i := -1
for {
recs, ok := <-cRecords
if !ok {
return nil
}
if !matchInt[i] {
_, err := p.Stdout.Writeln(marshaller(recs))
if err != nil {
p.Stderr.Writeln([]byte(err.Error()))
}
}
i++
}
case byColumnNumber:
for {
recs, ok := <-cRecords
if !ok {
return nil
}
var line []string
for i := range recs {
if !matchInt[i] {
line = append(line, recs[i])
}
}
if len(line) != 0 {
p.Stdout.Writeln(marshaller(line))
}
}
case byColumnName:
var (
lineNum int
headings = make(map[int]string)
)
for {
var line []string
recs, ok := <-cRecords
if !ok {
return nil
}
if lineNum == 0 {
for i := range recs {
headings[i] = recs[i]
if !matchStr[headings[i]] {
line = append(line, recs[i])
}
}
if len(line) != 0 {
p.Stdout.Writeln(marshaller(line))
}
} else {
for i := range recs {
if !matchStr[headings[i]] {
line = append(line, recs[i])
}
}
if len(line) != 0 {
p.Stdout.Writeln(marshaller(line))
}
}
lineNum++
}
default:
return errors.New("you haven't selected any rows / columns")
}
}*lang.Process: Process’s runtime state. Typically expressed as the variable p[]string: slice of parameters used in [ / ![chan []string: a channel for rows (each element in the slice is a column within the row). This allows tables to be stream-ablefunc(interface{}) ([]byte, error): data type marshaller functionReadArray() (type): Read from a data type one array element at a timeReadArrayWithType() (type): Read from a data type one array element at a time and return the elements contents and data typeReadIndex() (type): Data type handler for the index, [, builtinReadMap() (type): Treat data type as a key/value structure and read its contentsReadNotIndex() (type): Data type handler for the bang-prefixed index, ![, builtinWriteArray() (type): Write a data type, one array element at a timelang.IndexTemplateObject() (template API): Returns element(s) from a data structureThis document was generated from lang/stdio/interface_doc.yaml.
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