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scannerc.go
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scannerc.go
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package yaml
import (
"bytes"
"fmt"
)
// Introduction
// ************
//
// The following notes assume that you are familiar with the YAML specification
// (http://yaml.org/spec/cvs/current.html). We mostly follow it, although in
// some cases we are less restrictive that it requires.
//
// The process of transforming a YAML stream into a sequence of events is
// divided on two steps: Scanning and Parsing.
//
// The Scanner transforms the input stream into a sequence of tokens, while the
// parser transform the sequence of tokens produced by the Scanner into a
// sequence of parsing events.
//
// The Scanner is rather clever and complicated. The Parser, on the contrary,
// is a straightforward implementation of a recursive-descendant parser (or,
// LL(1) parser, as it is usually called).
//
// Actually there are two issues of Scanning that might be called "clever", the
// rest is quite straightforward. The issues are "block collection start" and
// "simple keys". Both issues are explained below in details.
//
// Here the Scanning step is explained and implemented. We start with the list
// of all the tokens produced by the Scanner together with short descriptions.
//
// Now, tokens:
//
// STREAM-START(encoding) # The stream start.
// STREAM-END # The stream end.
// VERSION-DIRECTIVE(major,minor) # The '%YAML' directive.
// TAG-DIRECTIVE(handle,prefix) # The '%TAG' directive.
// DOCUMENT-START # '---'
// DOCUMENT-END # '...'
// BLOCK-SEQUENCE-START # Indentation increase denoting a block
// BLOCK-MAPPING-START # sequence or a block mapping.
// BLOCK-END # Indentation decrease.
// FLOW-SEQUENCE-START # '['
// FLOW-SEQUENCE-END # ']'
// BLOCK-SEQUENCE-START # '{'
// BLOCK-SEQUENCE-END # '}'
// BLOCK-ENTRY # '-'
// FLOW-ENTRY # ','
// KEY # '?' or nothing (simple keys).
// VALUE # ':'
// ALIAS(anchor) # '*anchor'
// ANCHOR(anchor) # '&anchor'
// TAG(handle,suffix) # '!handle!suffix'
// SCALAR(value,style) # A scalar.
//
// The following two tokens are "virtual" tokens denoting the beginning and the
// end of the stream:
//
// STREAM-START(encoding)
// STREAM-END
//
// We pass the information about the input stream encoding with the
// STREAM-START token.
//
// The next two tokens are responsible for tags:
//
// VERSION-DIRECTIVE(major,minor)
// TAG-DIRECTIVE(handle,prefix)
//
// Example:
//
// %YAML 1.1
// %TAG ! !foo
// %TAG !yaml! tag:yaml.org,2002:
// ---
//
// The correspoding sequence of tokens:
//
// STREAM-START(utf-8)
// VERSION-DIRECTIVE(1,1)
// TAG-DIRECTIVE("!","!foo")
// TAG-DIRECTIVE("!yaml","tag:yaml.org,2002:")
// DOCUMENT-START
// STREAM-END
//
// Note that the VERSION-DIRECTIVE and TAG-DIRECTIVE tokens occupy a whole
// line.
//
// The document start and end indicators are represented by:
//
// DOCUMENT-START
// DOCUMENT-END
//
// Note that if a YAML stream contains an implicit document (without '---'
// and '...' indicators), no DOCUMENT-START and DOCUMENT-END tokens will be
// produced.
//
// In the following examples, we present whole documents together with the
// produced tokens.
//
// 1. An implicit document:
//
// 'a scalar'
//
// Tokens:
//
// STREAM-START(utf-8)
// SCALAR("a scalar",single-quoted)
// STREAM-END
//
// 2. An explicit document:
//
// ---
// 'a scalar'
// ...
//
// Tokens:
//
// STREAM-START(utf-8)
// DOCUMENT-START
// SCALAR("a scalar",single-quoted)
// DOCUMENT-END
// STREAM-END
//
// 3. Several documents in a stream:
//
// 'a scalar'
// ---
// 'another scalar'
// ---
// 'yet another scalar'
//
// Tokens:
//
// STREAM-START(utf-8)
// SCALAR("a scalar",single-quoted)
// DOCUMENT-START
// SCALAR("another scalar",single-quoted)
// DOCUMENT-START
// SCALAR("yet another scalar",single-quoted)
// STREAM-END
//
// We have already introduced the SCALAR token above. The following tokens are
// used to describe aliases, anchors, tag, and scalars:
//
// ALIAS(anchor)
// ANCHOR(anchor)
// TAG(handle,suffix)
// SCALAR(value,style)
//
// The following series of examples illustrate the usage of these tokens:
//
// 1. A recursive sequence:
//
// &A [ *A ]
//
// Tokens:
//
// STREAM-START(utf-8)
// ANCHOR("A")
// FLOW-SEQUENCE-START
// ALIAS("A")
// FLOW-SEQUENCE-END
// STREAM-END
//
// 2. A tagged scalar:
//
// !!float "3.14" # A good approximation.
//
// Tokens:
//
// STREAM-START(utf-8)
// TAG("!!","float")
// SCALAR("3.14",double-quoted)
// STREAM-END
//
// 3. Various scalar styles:
//
// --- # Implicit empty plain scalars do not produce tokens.
// --- a plain scalar
// --- 'a single-quoted scalar'
// --- "a double-quoted scalar"
// --- |-
// a literal scalar
// --- >-
// a folded
// scalar
//
// Tokens:
//
// STREAM-START(utf-8)
// DOCUMENT-START
// DOCUMENT-START
// SCALAR("a plain scalar",plain)
// DOCUMENT-START
// SCALAR("a single-quoted scalar",single-quoted)
// DOCUMENT-START
// SCALAR("a double-quoted scalar",double-quoted)
// DOCUMENT-START
// SCALAR("a literal scalar",literal)
// DOCUMENT-START
// SCALAR("a folded scalar",folded)
// STREAM-END
//
// Now it's time to review collection-related tokens. We will start with
// flow collections:
//
// FLOW-SEQUENCE-START
// FLOW-SEQUENCE-END
// FLOW-MAPPING-START
// FLOW-MAPPING-END
// FLOW-ENTRY
// KEY
// VALUE
//
// The tokens FLOW-SEQUENCE-START, FLOW-SEQUENCE-END, FLOW-MAPPING-START, and
// FLOW-MAPPING-END represent the indicators '[', ']', '{', and '}'
// correspondingly. FLOW-ENTRY represent the ',' indicator. Finally the
// indicators '?' and ':', which are used for denoting mapping keys and values,
// are represented by the KEY and VALUE tokens.
//
// The following examples show flow collections:
//
// 1. A flow sequence:
//
// [item 1, item 2, item 3]
//
// Tokens:
//
// STREAM-START(utf-8)
// FLOW-SEQUENCE-START
// SCALAR("item 1",plain)
// FLOW-ENTRY
// SCALAR("item 2",plain)
// FLOW-ENTRY
// SCALAR("item 3",plain)
// FLOW-SEQUENCE-END
// STREAM-END
//
// 2. A flow mapping:
//
// {
// a simple key: a value, # Note that the KEY token is produced.
// ? a complex key: another value,
// }
//
// Tokens:
//
// STREAM-START(utf-8)
// FLOW-MAPPING-START
// KEY
// SCALAR("a simple key",plain)
// VALUE
// SCALAR("a value",plain)
// FLOW-ENTRY
// KEY
// SCALAR("a complex key",plain)
// VALUE
// SCALAR("another value",plain)
// FLOW-ENTRY
// FLOW-MAPPING-END
// STREAM-END
//
// A simple key is a key which is not denoted by the '?' indicator. Note that
// the Scanner still produce the KEY token whenever it encounters a simple key.
//
// For scanning block collections, the following tokens are used (note that we
// repeat KEY and VALUE here):
//
// BLOCK-SEQUENCE-START
// BLOCK-MAPPING-START
// BLOCK-END
// BLOCK-ENTRY
// KEY
// VALUE
//
// The tokens BLOCK-SEQUENCE-START and BLOCK-MAPPING-START denote indentation
// increase that precedes a block collection (cf. the INDENT token in Python).
// The token BLOCK-END denote indentation decrease that ends a block collection
// (cf. the DEDENT token in Python). However YAML has some syntax pecularities
// that makes detections of these tokens more complex.
//
// The tokens BLOCK-ENTRY, KEY, and VALUE are used to represent the indicators
// '-', '?', and ':' correspondingly.
//
// The following examples show how the tokens BLOCK-SEQUENCE-START,
// BLOCK-MAPPING-START, and BLOCK-END are emitted by the Scanner:
//
// 1. Block sequences:
//
// - item 1
// - item 2
// -
// - item 3.1
// - item 3.2
// -
// key 1: value 1
// key 2: value 2
//
// Tokens:
//
// STREAM-START(utf-8)
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// SCALAR("item 1",plain)
// BLOCK-ENTRY
// SCALAR("item 2",plain)
// BLOCK-ENTRY
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// SCALAR("item 3.1",plain)
// BLOCK-ENTRY
// SCALAR("item 3.2",plain)
// BLOCK-END
// BLOCK-ENTRY
// BLOCK-MAPPING-START
// KEY
// SCALAR("key 1",plain)
// VALUE
// SCALAR("value 1",plain)
// KEY
// SCALAR("key 2",plain)
// VALUE
// SCALAR("value 2",plain)
// BLOCK-END
// BLOCK-END
// STREAM-END
//
// 2. Block mappings:
//
// a simple key: a value # The KEY token is produced here.
// ? a complex key
// : another value
// a mapping:
// key 1: value 1
// key 2: value 2
// a sequence:
// - item 1
// - item 2
//
// Tokens:
//
// STREAM-START(utf-8)
// BLOCK-MAPPING-START
// KEY
// SCALAR("a simple key",plain)
// VALUE
// SCALAR("a value",plain)
// KEY
// SCALAR("a complex key",plain)
// VALUE
// SCALAR("another value",plain)
// KEY
// SCALAR("a mapping",plain)
// BLOCK-MAPPING-START
// KEY
// SCALAR("key 1",plain)
// VALUE
// SCALAR("value 1",plain)
// KEY
// SCALAR("key 2",plain)
// VALUE
// SCALAR("value 2",plain)
// BLOCK-END
// KEY
// SCALAR("a sequence",plain)
// VALUE
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// SCALAR("item 1",plain)
// BLOCK-ENTRY
// SCALAR("item 2",plain)
// BLOCK-END
// BLOCK-END
// STREAM-END
//
// YAML does not always require to start a new block collection from a new
// line. If the current line contains only '-', '?', and ':' indicators, a new
// block collection may start at the current line. The following examples
// illustrate this case:
//
// 1. Collections in a sequence:
//
// - - item 1
// - item 2
// - key 1: value 1
// key 2: value 2
// - ? complex key
// : complex value
//
// Tokens:
//
// STREAM-START(utf-8)
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// SCALAR("item 1",plain)
// BLOCK-ENTRY
// SCALAR("item 2",plain)
// BLOCK-END
// BLOCK-ENTRY
// BLOCK-MAPPING-START
// KEY
// SCALAR("key 1",plain)
// VALUE
// SCALAR("value 1",plain)
// KEY
// SCALAR("key 2",plain)
// VALUE
// SCALAR("value 2",plain)
// BLOCK-END
// BLOCK-ENTRY
// BLOCK-MAPPING-START
// KEY
// SCALAR("complex key")
// VALUE
// SCALAR("complex value")
// BLOCK-END
// BLOCK-END
// STREAM-END
//
// 2. Collections in a mapping:
//
// ? a sequence
// : - item 1
// - item 2
// ? a mapping
// : key 1: value 1
// key 2: value 2
//
// Tokens:
//
// STREAM-START(utf-8)
// BLOCK-MAPPING-START
// KEY
// SCALAR("a sequence",plain)
// VALUE
// BLOCK-SEQUENCE-START
// BLOCK-ENTRY
// SCALAR("item 1",plain)
// BLOCK-ENTRY
// SCALAR("item 2",plain)
// BLOCK-END
// KEY
// SCALAR("a mapping",plain)
// VALUE
// BLOCK-MAPPING-START
// KEY
// SCALAR("key 1",plain)
// VALUE
// SCALAR("value 1",plain)
// KEY
// SCALAR("key 2",plain)
// VALUE
// SCALAR("value 2",plain)
// BLOCK-END
// BLOCK-END
// STREAM-END
//
// YAML also permits non-indented sequences if they are included into a block
// mapping. In this case, the token BLOCK-SEQUENCE-START is not produced:
//
// key:
// - item 1 # BLOCK-SEQUENCE-START is NOT produced here.
// - item 2
//
// Tokens:
//
// STREAM-START(utf-8)
// BLOCK-MAPPING-START
// KEY
// SCALAR("key",plain)
// VALUE
// BLOCK-ENTRY
// SCALAR("item 1",plain)
// BLOCK-ENTRY
// SCALAR("item 2",plain)
// BLOCK-END
//
// Ensure that the buffer contains the required number of characters.
// Return true on success, false on failure (reader error or memory error).
func cache(parser *yaml_parser_t, length int) bool {
// [Go] This was inlined: !cache(A, B) -> unread < B && !update(A, B)
return parser.unread >= length || yaml_parser_update_buffer(parser, length)
}
// Advance the buffer pointer.
func skip(parser *yaml_parser_t) {
parser.mark.index++
parser.mark.column++
parser.unread--
parser.buffer_pos += width(parser.buffer[parser.buffer_pos])
}
func skip_line(parser *yaml_parser_t) {
if is_crlf(parser.buffer, parser.buffer_pos) {
parser.mark.index += 2
parser.mark.column = 0
parser.mark.line++
parser.unread -= 2
parser.buffer_pos += 2
} else if is_break(parser.buffer, parser.buffer_pos) {
parser.mark.index++
parser.mark.column = 0
parser.mark.line++
parser.unread--
parser.buffer_pos += width(parser.buffer[parser.buffer_pos])
}
}
// Copy a character to a string buffer and advance pointers.
func read(parser *yaml_parser_t, s []byte) []byte {
w := width(parser.buffer[parser.buffer_pos])
if w == 0 {
panic("invalid character sequence")
}
if len(s) == 0 {
s = make([]byte, 0, 32)
}
if w == 1 && len(s)+w <= cap(s) {
s = s[:len(s)+1]
s[len(s)-1] = parser.buffer[parser.buffer_pos]
parser.buffer_pos++
} else {
s = append(s, parser.buffer[parser.buffer_pos:parser.buffer_pos+w]...)
parser.buffer_pos += w
}
parser.mark.index++
parser.mark.column++
parser.unread--
return s
}
// Copy a line break character to a string buffer and advance pointers.
func read_line(parser *yaml_parser_t, s []byte) []byte {
buf := parser.buffer
pos := parser.buffer_pos
switch {
case buf[pos] == '\r' && buf[pos+1] == '\n':
// CR LF . LF
s = append(s, '\n')
parser.buffer_pos += 2
parser.mark.index++
parser.unread--
case buf[pos] == '\r' || buf[pos] == '\n':
// CR|LF . LF
s = append(s, '\n')
parser.buffer_pos += 1
case buf[pos] == '\xC2' && buf[pos+1] == '\x85':
// NEL . LF
s = append(s, '\n')
parser.buffer_pos += 2
case buf[pos] == '\xE2' && buf[pos+1] == '\x80' && (buf[pos+2] == '\xA8' || buf[pos+2] == '\xA9'):
// LS|PS . LS|PS
s = append(s, buf[parser.buffer_pos:pos+3]...)
parser.buffer_pos += 3
default:
return s
}
parser.mark.index++
parser.mark.column = 0
parser.mark.line++
parser.unread--
return s
}
// Get the next token.
func yaml_parser_scan(parser *yaml_parser_t, token *yaml_token_t) bool {
// Erase the token object.
*token = yaml_token_t{} // [Go] Is this necessary?
// No tokens after STREAM-END or error.
if parser.stream_end_produced || parser.error != yaml_NO_ERROR {
return true
}
// Ensure that the tokens queue contains enough tokens.
if !parser.token_available {
if !yaml_parser_fetch_more_tokens(parser) {
return false
}
}
// Fetch the next token from the queue.
*token = parser.tokens[parser.tokens_head]
parser.tokens_head++
parser.tokens_parsed++
parser.token_available = false
if token.typ == yaml_STREAM_END_TOKEN {
parser.stream_end_produced = true
}
return true
}
// Set the scanner error and return false.
func yaml_parser_set_scanner_error(parser *yaml_parser_t, context string, context_mark yaml_mark_t, problem string) bool {
parser.error = yaml_SCANNER_ERROR
parser.context = context
parser.context_mark = context_mark
parser.problem = problem
parser.problem_mark = parser.mark
return false
}
func yaml_parser_set_scanner_tag_error(parser *yaml_parser_t, directive bool, context_mark yaml_mark_t, problem string) bool {
context := "while parsing a tag"
if directive {
context = "while parsing a %TAG directive"
}
return yaml_parser_set_scanner_error(parser, context, context_mark, "did not find URI escaped octet")
}
func trace(args ...interface{}) func() {
pargs := append([]interface{}{"+++"}, args...)
fmt.Println(pargs...)
pargs = append([]interface{}{"---"}, args...)
return func() { fmt.Println(pargs...) }
}
// Ensure that the tokens queue contains at least one token which can be
// returned to the Parser.
func yaml_parser_fetch_more_tokens(parser *yaml_parser_t) bool {
// While we need more tokens to fetch, do it.
for {
// Check if we really need to fetch more tokens.
need_more_tokens := false
if parser.tokens_head == len(parser.tokens) {
// Queue is empty.
need_more_tokens = true
} else {
// Check if any potential simple key may occupy the head position.
if !yaml_parser_stale_simple_keys(parser) {
return false
}
for i := range parser.simple_keys {
simple_key := &parser.simple_keys[i]
if simple_key.possible && simple_key.token_number == parser.tokens_parsed {
need_more_tokens = true
break
}
}
}
// We are finished.
if !need_more_tokens {
break
}
// Fetch the next token.
if !yaml_parser_fetch_next_token(parser) {
return false
}
}
parser.token_available = true
return true
}
// The dispatcher for token fetchers.
func yaml_parser_fetch_next_token(parser *yaml_parser_t) bool {
// Ensure that the buffer is initialized.
if parser.unread < 1 && !yaml_parser_update_buffer(parser, 1) {
return false
}
// Check if we just started scanning. Fetch STREAM-START then.
if !parser.stream_start_produced {
return yaml_parser_fetch_stream_start(parser)
}
// Eat whitespaces and comments until we reach the next token.
if !yaml_parser_scan_to_next_token(parser) {
return false
}
// Remove obsolete potential simple keys.
if !yaml_parser_stale_simple_keys(parser) {
return false
}
// Check the indentation level against the current column.
if !yaml_parser_unroll_indent(parser, parser.mark.column) {
return false
}
// Ensure that the buffer contains at least 4 characters. 4 is the length
// of the longest indicators ('--- ' and '... ').
if parser.unread < 4 && !yaml_parser_update_buffer(parser, 4) {
return false
}
// Is it the end of the stream?
if is_z(parser.buffer, parser.buffer_pos) {
return yaml_parser_fetch_stream_end(parser)
}
// Is it a directive?
if parser.mark.column == 0 && parser.buffer[parser.buffer_pos] == '%' {
return yaml_parser_fetch_directive(parser)
}
buf := parser.buffer
pos := parser.buffer_pos
// Is it the document start indicator?
if parser.mark.column == 0 && buf[pos] == '-' && buf[pos+1] == '-' && buf[pos+2] == '-' && is_blankz(buf, pos+3) {
return yaml_parser_fetch_document_indicator(parser, yaml_DOCUMENT_START_TOKEN)
}
// Is it the document end indicator?
if parser.mark.column == 0 && buf[pos] == '.' && buf[pos+1] == '.' && buf[pos+2] == '.' && is_blankz(buf, pos+3) {
return yaml_parser_fetch_document_indicator(parser, yaml_DOCUMENT_END_TOKEN)
}
// Is it the flow sequence start indicator?
if buf[pos] == '[' {
return yaml_parser_fetch_flow_collection_start(parser, yaml_FLOW_SEQUENCE_START_TOKEN)
}
// Is it the flow mapping start indicator?
if parser.buffer[parser.buffer_pos] == '{' {
return yaml_parser_fetch_flow_collection_start(parser, yaml_FLOW_MAPPING_START_TOKEN)
}
// Is it the flow sequence end indicator?
if parser.buffer[parser.buffer_pos] == ']' {
return yaml_parser_fetch_flow_collection_end(parser,
yaml_FLOW_SEQUENCE_END_TOKEN)
}
// Is it the flow mapping end indicator?
if parser.buffer[parser.buffer_pos] == '}' {
return yaml_parser_fetch_flow_collection_end(parser,
yaml_FLOW_MAPPING_END_TOKEN)
}
// Is it the flow entry indicator?
if parser.buffer[parser.buffer_pos] == ',' {
return yaml_parser_fetch_flow_entry(parser)
}
// Is it the block entry indicator?
if parser.buffer[parser.buffer_pos] == '-' && is_blankz(parser.buffer, parser.buffer_pos+1) {
return yaml_parser_fetch_block_entry(parser)
}
// Is it the key indicator?
if parser.buffer[parser.buffer_pos] == '?' && (parser.flow_level > 0 || is_blankz(parser.buffer, parser.buffer_pos+1)) {
return yaml_parser_fetch_key(parser)
}
// Is it the value indicator?
if parser.buffer[parser.buffer_pos] == ':' && (parser.flow_level > 0 || is_blankz(parser.buffer, parser.buffer_pos+1)) {
return yaml_parser_fetch_value(parser)
}
// Is it an alias?
if parser.buffer[parser.buffer_pos] == '*' {
return yaml_parser_fetch_anchor(parser, yaml_ALIAS_TOKEN)
}
// Is it an anchor?
if parser.buffer[parser.buffer_pos] == '&' {
return yaml_parser_fetch_anchor(parser, yaml_ANCHOR_TOKEN)
}
// Is it a tag?
if parser.buffer[parser.buffer_pos] == '!' {
return yaml_parser_fetch_tag(parser)
}
// Is it a literal scalar?
if parser.buffer[parser.buffer_pos] == '|' && parser.flow_level == 0 {
return yaml_parser_fetch_block_scalar(parser, true)
}
// Is it a folded scalar?
if parser.buffer[parser.buffer_pos] == '>' && parser.flow_level == 0 {
return yaml_parser_fetch_block_scalar(parser, false)
}
// Is it a single-quoted scalar?
if parser.buffer[parser.buffer_pos] == '\'' {
return yaml_parser_fetch_flow_scalar(parser, true)
}
// Is it a double-quoted scalar?
if parser.buffer[parser.buffer_pos] == '"' {
return yaml_parser_fetch_flow_scalar(parser, false)
}
// Is it a plain scalar?
//
// A plain scalar may start with any non-blank characters except
//
// '-', '?', ':', ',', '[', ']', '{', '}',
// '#', '&', '*', '!', '|', '>', '\'', '\"',
// '%', '@', '`'.
//
// In the block context (and, for the '-' indicator, in the flow context
// too), it may also start with the characters
//
// '-', '?', ':'
//
// if it is followed by a non-space character.
//
// The last rule is more restrictive than the specification requires.
// [Go] Make this logic more reasonable.
//switch parser.buffer[parser.buffer_pos] {
//case '-', '?', ':', ',', '?', '-', ',', ':', ']', '[', '}', '{', '&', '#', '!', '*', '>', '|', '"', '\'', '@', '%', '-', '`':
//}
if !(is_blankz(parser.buffer, parser.buffer_pos) || parser.buffer[parser.buffer_pos] == '-' ||
parser.buffer[parser.buffer_pos] == '?' || parser.buffer[parser.buffer_pos] == ':' ||
parser.buffer[parser.buffer_pos] == ',' || parser.buffer[parser.buffer_pos] == '[' ||
parser.buffer[parser.buffer_pos] == ']' || parser.buffer[parser.buffer_pos] == '{' ||
parser.buffer[parser.buffer_pos] == '}' || parser.buffer[parser.buffer_pos] == '#' ||
parser.buffer[parser.buffer_pos] == '&' || parser.buffer[parser.buffer_pos] == '*' ||
parser.buffer[parser.buffer_pos] == '!' || parser.buffer[parser.buffer_pos] == '|' ||
parser.buffer[parser.buffer_pos] == '>' || parser.buffer[parser.buffer_pos] == '\'' ||
parser.buffer[parser.buffer_pos] == '"' || parser.buffer[parser.buffer_pos] == '%' ||
parser.buffer[parser.buffer_pos] == '@' || parser.buffer[parser.buffer_pos] == '`') ||
(parser.buffer[parser.buffer_pos] == '-' && !is_blank(parser.buffer, parser.buffer_pos+1)) ||
(parser.flow_level == 0 &&
(parser.buffer[parser.buffer_pos] == '?' || parser.buffer[parser.buffer_pos] == ':') &&
!is_blankz(parser.buffer, parser.buffer_pos+1)) {
return yaml_parser_fetch_plain_scalar(parser)
}
// If we don't determine the token type so far, it is an error.
return yaml_parser_set_scanner_error(parser,
"while scanning for the next token", parser.mark,
"found character that cannot start any token")
}
// Check the list of potential simple keys and remove the positions that
// cannot contain simple keys anymore.
func yaml_parser_stale_simple_keys(parser *yaml_parser_t) bool {
// Check for a potential simple key for each flow level.
for i := range parser.simple_keys {
simple_key := &parser.simple_keys[i]
// The specification requires that a simple key
//
// - is limited to a single line,
// - is shorter than 1024 characters.
if simple_key.possible && (simple_key.mark.line < parser.mark.line || simple_key.mark.index+1024 < parser.mark.index) {
// Check if the potential simple key to be removed is required.
if simple_key.required {
return yaml_parser_set_scanner_error(parser,
"while scanning a simple key", simple_key.mark,
"could not find expected ':'")
}
simple_key.possible = false
}
}
return true
}
// Check if a simple key may start at the current position and add it if
// needed.
func yaml_parser_save_simple_key(parser *yaml_parser_t) bool {
// A simple key is required at the current position if the scanner is in
// the block context and the current column coincides with the indentation
// level.
required := parser.flow_level == 0 && parser.indent == parser.mark.column
// A simple key is required only when it is the first token in the current
// line. Therefore it is always allowed. But we add a check anyway.
if required && !parser.simple_key_allowed {
panic("should not happen")
}
//
// If the current position may start a simple key, save it.
//
if parser.simple_key_allowed {
simple_key := yaml_simple_key_t{
possible: true,
required: required,
token_number: parser.tokens_parsed + (len(parser.tokens) - parser.tokens_head),
}
simple_key.mark = parser.mark
if !yaml_parser_remove_simple_key(parser) {
return false
}
parser.simple_keys[len(parser.simple_keys)-1] = simple_key
}
return true
}
// Remove a potential simple key at the current flow level.
func yaml_parser_remove_simple_key(parser *yaml_parser_t) bool {
i := len(parser.simple_keys) - 1
if parser.simple_keys[i].possible {
// If the key is required, it is an error.
if parser.simple_keys[i].required {
return yaml_parser_set_scanner_error(parser,
"while scanning a simple key", parser.simple_keys[i].mark,
"could not find expected ':'")
}
}
// Remove the key from the stack.
parser.simple_keys[i].possible = false
return true
}
// Increase the flow level and resize the simple key list if needed.
func yaml_parser_increase_flow_level(parser *yaml_parser_t) bool {
// Reset the simple key on the next level.
parser.simple_keys = append(parser.simple_keys, yaml_simple_key_t{})
// Increase the flow level.
parser.flow_level++
return true
}
// Decrease the flow level.
func yaml_parser_decrease_flow_level(parser *yaml_parser_t) bool {
if parser.flow_level > 0 {
parser.flow_level--
parser.simple_keys = parser.simple_keys[:len(parser.simple_keys)-1]
}
return true
}
// Push the current indentation level to the stack and set the new level
// the current column is greater than the indentation level. In this case,
// append or insert the specified token into the token queue.
func yaml_parser_roll_indent(parser *yaml_parser_t, column, number int, typ yaml_token_type_t, mark yaml_mark_t) bool {
// In the flow context, do nothing.
if parser.flow_level > 0 {
return true
}
if parser.indent < column {
// Push the current indentation level to the stack and set the new
// indentation level.
parser.indents = append(parser.indents, parser.indent)
parser.indent = column
// Create a token and insert it into the queue.
token := yaml_token_t{
typ: typ,
start_mark: mark,
end_mark: mark,
}
if number > -1 {
number -= parser.tokens_parsed
}
yaml_insert_token(parser, number, &token)
}
return true
}
// Pop indentation levels from the indents stack until the current level
// becomes less or equal to the column. For each intendation level, append
// the BLOCK-END token.
func yaml_parser_unroll_indent(parser *yaml_parser_t, column int) bool {
// In the flow context, do nothing.
if parser.flow_level > 0 {
return true
}
// Loop through the intendation levels in the stack.
for parser.indent > column {
// Create a token and append it to the queue.
token := yaml_token_t{
typ: yaml_BLOCK_END_TOKEN,
start_mark: parser.mark,
end_mark: parser.mark,
}
yaml_insert_token(parser, -1, &token)
// Pop the indentation level.
parser.indent = parser.indents[len(parser.indents)-1]
parser.indents = parser.indents[:len(parser.indents)-1]
}
return true
}
// Initialize the scanner and produce the STREAM-START token.
func yaml_parser_fetch_stream_start(parser *yaml_parser_t) bool {
// Set the initial indentation.
parser.indent = -1
// Initialize the simple key stack.
parser.simple_keys = append(parser.simple_keys, yaml_simple_key_t{})
// A simple key is allowed at the beginning of the stream.
parser.simple_key_allowed = true