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selector_parser.go
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selector_parser.go
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package abi
import (
"fmt"
)
type SelectorMarshaling struct {
Name string `json:"name"`
Type string `json:"type"`
Inputs []ArgumentMarshaling `json:"inputs"`
}
func isDigit(c byte) bool {
return c >= '0' && c <= '9'
}
func isAlpha(c byte) bool {
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
}
func isIdentifierSymbol(c byte) bool {
return c == '$' || c == '_'
}
func parseToken(unescapedSelector string, isIdent bool) (string, string, error) {
if len(unescapedSelector) == 0 {
return "", "", fmt.Errorf("empty token")
}
firstChar := unescapedSelector[0]
position := 1
if !(isAlpha(firstChar) || (isIdent && isIdentifierSymbol(firstChar))) {
return "", "", fmt.Errorf("invalid token start: %c", firstChar)
}
for position < len(unescapedSelector) {
char := unescapedSelector[position]
if !(isAlpha(char) || isDigit(char) || (isIdent && isIdentifierSymbol(char))) {
break
}
position++
}
return unescapedSelector[:position], unescapedSelector[position:], nil
}
func parseIdentifier(unescapedSelector string) (string, string, error) {
return parseToken(unescapedSelector, true)
}
func parseElementaryType(unescapedSelector string) (string, string, error) {
parsedType, rest, err := parseToken(unescapedSelector, false)
if err != nil {
return "", "", fmt.Errorf("failed to parse elementary type: %v", err)
}
// handle arrays
for len(rest) > 0 && rest[0] == '[' {
parsedType = parsedType + string(rest[0])
rest = rest[1:]
for len(rest) > 0 && isDigit(rest[0]) {
parsedType = parsedType + string(rest[0])
rest = rest[1:]
}
if len(rest) == 0 || rest[0] != ']' {
return "", "", fmt.Errorf("failed to parse array: expected ']', got %c", unescapedSelector[0])
}
parsedType = parsedType + string(rest[0])
rest = rest[1:]
}
return parsedType, rest, nil
}
func parseCompositeType(unescapedSelector string) ([]interface{}, string, error) {
if len(unescapedSelector) == 0 || unescapedSelector[0] != '(' {
return nil, "", fmt.Errorf("expected '(', got %c", unescapedSelector[0])
}
parsedType, rest, err := parseType(unescapedSelector[1:])
if err != nil {
return nil, "", fmt.Errorf("failed to parse type: %v", err)
}
result := []interface{}{parsedType}
for len(rest) > 0 && rest[0] != ')' {
parsedType, rest, err = parseType(rest[1:])
if err != nil {
return nil, "", fmt.Errorf("failed to parse type: %v", err)
}
result = append(result, parsedType)
}
if len(rest) == 0 || rest[0] != ')' {
return nil, "", fmt.Errorf("expected ')', got '%s'", rest)
}
return result, rest[1:], nil
}
func parseType(unescapedSelector string) (interface{}, string, error) {
if len(unescapedSelector) == 0 {
return nil, "", fmt.Errorf("empty type")
}
if unescapedSelector[0] == '(' {
return parseCompositeType(unescapedSelector)
} else {
return parseElementaryType(unescapedSelector)
}
}
func assembleArgs(args []interface{}) ([]ArgumentMarshaling, error) {
arguments := make([]ArgumentMarshaling, 0)
for i, arg := range args {
// generate dummy name to avoid unmarshal issues
name := fmt.Sprintf("name%d", i)
if s, ok := arg.(string); ok {
arguments = append(arguments, ArgumentMarshaling{name, s, s, nil, false})
} else if components, ok := arg.([]interface{}); ok {
subArgs, err := assembleArgs(components)
if err != nil {
return nil, fmt.Errorf("failed to assemble components: %v", err)
}
arguments = append(arguments, ArgumentMarshaling{name, "tuple", "tuple", subArgs, false})
} else {
return nil, fmt.Errorf("failed to assemble args: unexpected type %T", arg)
}
}
return arguments, nil
}
// ParseSelector converts a method selector into a struct that can be JSON encoded
// and consumed by other functions in this package.
// Note, although uppercase letters are not part of the ABI spec, this function
// still accepts it as the general format is valid.
func ParseSelector(unescapedSelector string) (SelectorMarshaling, error) {
name, rest, err := parseIdentifier(unescapedSelector)
if err != nil {
return SelectorMarshaling{}, fmt.Errorf("failed to parse selector '%s': %v", unescapedSelector, err)
}
args := []interface{}{}
if len(rest) >= 2 && rest[0] == '(' && rest[1] == ')' {
rest = rest[2:]
} else {
args, rest, err = parseCompositeType(rest)
if err != nil {
return SelectorMarshaling{}, fmt.Errorf("failed to parse selector '%s': %v", unescapedSelector, err)
}
}
if len(rest) > 0 {
return SelectorMarshaling{}, fmt.Errorf("failed to parse selector '%s': unexpected string '%s'", unescapedSelector, rest)
}
// Reassemble the fake ABI and constuct the JSON
fakeArgs, err := assembleArgs(args)
if err != nil {
return SelectorMarshaling{}, fmt.Errorf("failed to parse selector: %v", err)
}
return SelectorMarshaling{name, "function", fakeArgs}, nil
}