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package squirrel
import (
"bytes"
"fmt"
"strings"
)
// PlaceholderFormat is the interface that wraps the ReplacePlaceholders method.
//
// ReplacePlaceholders takes a SQL statement and replaces each question mark
// placeholder with a (possibly different) SQL placeholder.
type PlaceholderFormat interface {
ReplacePlaceholders(sql string) (string, error)
}
type placeholderDebugger interface {
debugPlaceholder() string
}
var (
// Question is a PlaceholderFormat instance that leaves placeholders as
// question marks.
Question = questionFormat{}
// Dollar is a PlaceholderFormat instance that replaces placeholders with
// dollar-prefixed positional placeholders (e.g. $1, $2, $3).
Dollar = dollarFormat{}
// Colon is a PlaceholderFormat instance that replaces placeholders with
// colon-prefixed positional placeholders (e.g. :1, :2, :3).
Colon = colonFormat{}
// AtP is a PlaceholderFormat instance that replaces placeholders with
// "@p"-prefixed positional placeholders (e.g. @p1, @p2, @p3).
AtP = atpFormat{}
)
type questionFormat struct{}
func (questionFormat) ReplacePlaceholders(sql string) (string, error) {
return sql, nil
}
func (questionFormat) debugPlaceholder() string {
return "?"
}
type dollarFormat struct{}
func (dollarFormat) ReplacePlaceholders(sql string) (string, error) {
return replacePositionalPlaceholders(sql, "$")
}
func (dollarFormat) debugPlaceholder() string {
return "$"
}
type colonFormat struct{}
func (colonFormat) ReplacePlaceholders(sql string) (string, error) {
return replacePositionalPlaceholders(sql, ":")
}
func (colonFormat) debugPlaceholder() string {
return ":"
}
type atpFormat struct{}
func (atpFormat) ReplacePlaceholders(sql string) (string, error) {
return replacePositionalPlaceholders(sql, "@p")
}
func (atpFormat) debugPlaceholder() string {
return "@p"
}
// Placeholders returns a string with count ? placeholders joined with commas.
func Placeholders(count int) string {
if count < 1 {
return ""
}
return strings.Repeat(",?", count)[1:]
}
func replacePositionalPlaceholders(sql, prefix string) (string, error) {
buf := &bytes.Buffer{}
i := 0
for {
p := strings.Index(sql, "?")
if p == -1 {
break
}
if len(sql[p:]) > 1 && sql[p:p+2] == "??" { // escape ?? => ?
buf.WriteString(sql[:p])
buf.WriteString("?")
if len(sql[p:]) == 1 {
break
}
sql = sql[p+2:]
} else {
i++
buf.WriteString(sql[:p])
fmt.Fprintf(buf, "%s%d", prefix, i)
sql = sql[p+1:]
}
}
buf.WriteString(sql)
return buf.String(), nil
}
|
