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media_type.cr
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media_type.cr
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require "uri"
require "http"
require "mime"
module MIME
# A `MediaType` describes a MIME content type with optional parameters.
struct MediaType
getter media_type : String
# Creates a new `MediaType` instance.
def initialize(@media_type, @params = {} of String => String)
@params.each_key do |name|
raise Error.new("Invalid parameter name #{name.inspect}") unless MIME::MediaType.token? name
end
end
def to_s(io : IO) : Nil
io << media_type
@params.each do |key, value|
io << "; "
io << key.downcase << '='
if MIME::MediaType.token? value
io << value
else
io << '"'
MIME::MediaType.quote_string(value, io)
io << '"'
end
end
end
# Returns the value for the parameter given by *key*. If not found, raises `KeyError`.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.parse("text/plain; charset=UTF-8")["charset"] # => "UTF-8"
# MIME::MediaType.parse("text/plain; charset=UTF-8")["foo"] # raises KeyError
# ```
def [](key : String) : String
@params[key]
end
# Returns the value for the parameter given by *key*. If not found, returns `nil`.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.parse("text/plain; charset=UTF-8")["charset"]? # => "UTF-8"
# MIME::MediaType.parse("text/plain; charset=UTF-8")["foo"]? # => nil
# ```
def []?(key : String) : String?
@params[key]?
end
# Sets the value of parameter *key* to the given value.
#
# ```
# require "mime/media_type"
#
# mime_type = MIME::MediaType.parse("x-application/example")
# mime_type["foo"] = "bar"
# mime_type["foo"] # => "bar"
# ```
def []=(key : String, value : String)
raise Error.new("Invalid parameter name") unless MIME::MediaType.token? key
@params[key] = value
end
# Returns the value for the parameter given by *key*, or when not found the value given by *default*.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.parse("x-application/example").fetch("foo", "baz") # => "baz"
# MIME::MediaType.parse("x-application/example; foo=bar").fetch("foo", "baz") # => "bar"
# ```
def fetch(key : String, default)
@params.fetch(key, default)
end
# Returns the value for the parameter given by *key*, or when not found calls the given block with the *key*.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.parse("x-application/example").fetch("foo") { |key| key } # => "foo"
# MIME::MediaType.parse("x-application/example; foo=bar").fetch("foo") { |key| key } # => "bar"
# ```
def fetch(key : String, &block : String -> _)
@params.fetch(key) { |key| yield key }
end
# Calls the given block for each parameter and passes in the key and the value.
def each_parameter(&block : String, String -> _) : Nil
@params.each do |key, value|
yield key, value
end
end
# Returns an iterator over the parameter which behaves like an `Iterator` returning a `Tuple` of key and value.
def each_parameter : Iterator(Tuple(String, String))
@params.each
end
# First component of `media_type`.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.new("text/plain").type # => "text"
# MIME::MediaType.new("foo").type # => "foo"
# ```
#
def type : String
index = media_type.byte_index('/'.ord) || media_type.bytesize
media_type.byte_slice(0, index)
end
# Second component of `media_type` or `nil`.
#
# ```
# require "mime/media_type"
#
# MIME::MediaType.new("text/plain").sub_type # => "plain"
# MIME::MediaType.new("foo").sub_type # => nil
# ```
def sub_type : String?
index = media_type.byte_index('/'.ord) || return
media_type.byte_slice(index + 1, media_type.bytesize - index - 1)
end
# Parses a MIME type string representation including any optional parameters,
# per RFC 1521.
# Media types are the values in `Content-Type` and `Content-Disposition` HTTP
# headers (RFC 2183).
#
# Media type is lowercased and trimmed of whitespace. Param keys are lowercased.
#
# Raises `MIME::Error` on error.
def self.parse(string : String) : MediaType
parse_impl(string) { |err| raise MIME::Error.new("Parsing error: #{err} (#{string.dump})") }
end
# Parses a MIME type string representation including any optional parameters,
# per RFC 1521.
# Media types are the values in `Content-Type` and `Content-Disposition` HTTP
# headers (RFC 2183).
#
# Media type is lowercased and trimmed of whitespace. Param keys are lowercased.
#
# Returns `nil` on error.
def self.parse?(string : String) : MediaType?
parse_impl(string) { return nil }
end
# This methods parses a MIME media type according to RFC 2231
private def self.parse_impl(string : String, &block : String -> NoReturn)
reader = Char::Reader.new(string)
# 1. Reading the type and subtype, separated by a '/'
# media_type := type "/" sub_type
sub_type_start = -1 # invalid value to detect if sub type start was read
while reader.has_next?
char = reader.current_char
if char == ';'
# when ';' is reached, the media type is finished
# optional parameters may follow
break
elsif char == '/'
# Abort if there had already been a '/'
yield "Invalid '/' at #{reader.pos}" if sub_type_start > -1
# The separator between type and subtype has been reached
sub_type_start = reader.pos
reader.next_char
elsif token?(char)
reader.next_char
else
yield "Invalid character '#{char}' at #{reader.pos}"
end
end
# string is empty or first character was a ';'
yield "Missing media type" if reader.pos == 0
mediatype = string.byte_slice(0, reader.pos).strip.downcase
# string contained only whitespace as media type
yield "Missing media type" if mediatype.empty?
# 2. Consume parameters, consisting of attribute-value pairs
# parameters := *( ";" parameter)
# parameter := attribute "=" value
# Stores regular attribute-value pairs
params = {} of String => String
# Stores extended parameters with continuation values
continuation = Hash(String, Hash(String, String)).new do |hash, key|
hash[key] = {} of String => String
end
while reader.has_next?
# Consume optional whitespace
reader = consume_whitespace(reader)
break unless reader.has_next?
# ';' has not been consumed previously
reader.next_char
# Consume optional whitespace
reader = consume_whitespace(reader)
break unless reader.has_next?
key_start = reader.pos
# Consume attribute name and break at '='
while reader.has_next?
case char = reader.current_char
when ';'
yield "Invalid ';' at #{reader.pos}, expecting '='"
when '='
break
else
unless token?(char)
yield "Invalid character '#{char}' at #{reader.pos}"
end
reader.next_char
end
end
# Read the attribute name into a variable. It is case-insensitive and
# might be surrounded by whitespace, hence `.rstrip.downcase`.
key = string.byte_slice(key_start, reader.pos - key_start).rstrip.downcase
yield "Missing attribute name at #{key_start}" if key.empty?
# Consume '='
if reader.has_next?
reader.next_char
else
yield "Missing attribute value at #{reader.pos}"
end
# '*' designates an extended parameter name
# It is not yet processed but extended parameters are added to a
# special `continuation` map instead of `params` for later processing.
base_key, star, section = key.partition('*')
if star.empty?
if params.has_key?(key)
yield "Duplicate key '#{key}' at #{key_start}"
end
# Consume parameter value
reader, value = parse_parameter_value(reader) { |err| yield err }
# Add the attribute-value pair to `params`.
params[key] = value
else
# Remove whitespace surrounding '*'
base_key = base_key.rstrip
section = section.lstrip
section.each_char_with_index do |char, index|
unless char.ascii_number? || (char == '*' && index == section.bytesize - 1)
yield "Invalid key '#{key}' at #{key_start}"
end
end
# TODO: Using a different data structure than `Hash` for storing
# continuation sections could improve performance.
normalized_key = "#{base_key}*#{section}"
continuation_map = continuation[base_key]
if continuation_map.has_key?(normalized_key)
yield "Duplicate key '#{key}' at #{key_start}"
end
# Consume parameter value
reader, value = parse_parameter_value(reader) { |err| yield err }
# Add the attribute-value pair to `continuation` map.
continuation_map[normalized_key] = value
end
end
# 3. Resolve continuation parameters
#
# extended-parameter := (extended-initial-name "=" extended-value) /
# (extended-other-names "=" extended-other-values)
#
# initial-section := "*0"
#
# other-sections := "*" ("1" / "2" / "3" / "4" / "5" /
# "6" / "7" / "8" / "9") *DIGIT)
#
# extended-initial-name := attribute [initial-section] "*"
#
# extended-other-names := attribute other-sections "*"
#
# extended-initial-value := [charset] "'" [language] "'" extended-other-values
#
# extended-other-values := *(ext-octet / attribute-char)
continuation.each do |base_key, pieces|
# `#{base_key}*` is an extended-initial-name without initial-section.
# This is not the start of a continuation, just a single encoded value.
if value = pieces["#{base_key}*"]?
if decoded = decode_rfc2231(value)
params[base_key] = decoded
end
next
end
# All other pieces are extended-parameter and need to be sequentially
# ordered by section number
valid = false
composite_value = String.build do |io|
counter = 0
loop do
part_key = "#{base_key}*#{counter}"
if part = pieces[part_key]?
valid = true
io << part
elsif part = pieces["#{part_key}*"]?
valid = true
io << decode_rfc2231(part) || next
else
break
end
counter += 1
end
end
if valid
params[base_key] = composite_value
else
# TODO: Not sure if invalid parameter should error or just be ignored.
# yield "Invalid extended parameter: '#{base_key}'"
end
end
# text types should automatically use UTF-8 charset unless specified differently.
if mediatype.starts_with?("text/")
params["charset"] ||= "utf-8"
end
MediaType.new mediatype, params
end
private def self.parse_parameter_value(reader)
reader = consume_whitespace(reader)
# Quoted value.
if reader.current_char == '"'
reader.next_char
quoted = true
waiting_for_closing_quote = true
else
quoted = false
waiting_for_closing_quote = false
end
value = String.build do |io|
# Set positions for copying data from reader string to `io` in bulk.
value_start = reader.pos
value_end = reader.pos
while reader.has_next?
case char = reader.current_char
when ';'
break unless quoted
reader.next_char
when '"'
yield "Unexpected '\"' at #{reader.pos}" unless waiting_for_closing_quote
waiting_for_closing_quote = false
break
when '\\'
reader.next_char
char = reader.current_char
# Escape `\\` and `\"`
if char == '\\' || (quoted && char == '"')
# Write everything before the escaping backslash to io, then set
# `value_start` to the position of the escaped character, thus it
# will be included in the next write.
# This essentially skips writing the escaping backslash.
io.write reader.string.to_slice[value_start, reader.pos - value_start - 1]
value_start = reader.pos
reader.next_char
end
when '='
if quoted
reader.next_char
else
yield "Unexpected '=' at #{reader.pos}"
end
else
reader.next_char
end
end
if quoted
if waiting_for_closing_quote
yield "Unclosed quote at #{reader.pos}"
end
# Set position for final bulk copy.
value_end = reader.pos
reader.next_char
reader = consume_whitespace(reader)
if reader.has_next? && reader.current_char != ';'
yield "Invalid character '#{reader.current_char}' at #{reader.pos}, expecting ';'"
end
else
# remove right-hand-side whitespace when unquoted
# 1. Step one character back to check for whitespace.
reader.previous_char if reader.has_previous?
# 2. Remove whitespace.
while reader.has_previous? && reader.current_char.ascii_whitespace?
reader.previous_char
end
# 3. Step one character ahead again.
reader.next_char
value_end = reader.pos
end
io.write reader.string.to_slice[value_start, value_end - value_start]
end
return reader, value
end
private def self.decode_rfc2231(encoded : String)
encoding, split1, rest = encoded.partition('\'')
lang, split2, value = rest.partition('\'')
return if encoding.empty? || value.empty?
encoding = encoding.downcase
IO::Memory.new.tap do |io|
io.set_encoding encoding
reader = Char::Reader.new(value)
while reader.has_next?
case char = reader.current_char
when '%'
first = reader.next_char.to_i?(16) || return
second = reader.next_char.to_i?(16) || return
num = first << 4 | second
io.write_byte num.to_u8
reader.next_char
else
io << char
reader.next_char
end
end
end.rewind.gets_to_end
end
private def self.consume_whitespace(reader)
while reader.current_char.ascii_whitespace?
reader.next_char
end
reader
end
# :nodoc:
def self.token?(char : Char)
!TSPECIAL_CHARACTERS.includes?(char) && 0x20 <= char.ord < 0x7F
end
# :nodoc:
def self.token?(string)
string.each_char.all? { |char| token? char }
end
# :nodoc:
def self.quote_string(string, io)
string.each_byte do |byte|
case byte
when '"'.ord, '\\'.ord
io << '\\'
when 0x00..0x1F, 0x7F
raise ArgumentError.new("String contained invalid character #{byte.chr.inspect}")
else
# leave the byte as is
end
io.write_byte byte
end
end
end
end