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riff.nim
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## :Author: John Novak <john@johnnovak.net>
##
## [**nim-riff** is a library for reading and writing [Resource Interchange File Format (RIFF)](https://en.wikipedia.org/wiki/Resource_Interchange_File_Format)
## files.
##
## Main features:
## * Reading/writing of little-endian (`RIFF`) and big-endian (`RIFX`) RIFF
## files
## * Strict adherence to the RIFF standard
## * Convenient helper methods to navigate the chunk hierarchy
## * Cursor support
##
## Please refer to the [guide](https://github.com/johnnovak/nim-riff?tab=readme-ov-file#usage)
## and [examples](https://github.com/johnnovak/nim-riff/tree/master/examples)
## on how to use the library.
##
## Visit the project's GitHub repository for further info:
## https://github.com/johnnovak/nim-riff
##
import std/strformat
import std/strutils
import std/tables
import binstreams
# {{{ References
# ==============
#
# [1] "EA IFF 85" Standard for Interchange Format Files
# (Electronic Arts, 1985)
# https://wiki.amigaos.net/wiki/EA_IFF_85_Standard_for_Interchange_Format_Files
# http://www.martinreddy.net/gfx/2d/IFF.txt
#
# [2] A Quick Introduction to IFF
# (AmigaOS Documentation Wiki)
# https://wiki.amigaos.net/wiki/A_Quick_Introduction_to_IFF
#
# [3] Resource Interchange File Format
# (Wikipedia)
# https://en.wikipedia.org/wiki/Resource_Interchange_File_Format
#
# [4] RIFF (Resource Interchange File Format)
# (Digital Preservation. Library of Congress)
# https://www.loc.gov/preservation/digital/formats/fdd/fdd000025.shtml
#
# [5] Multimedia Programming Interface and Data Specifications 1.0
# (Microsoft / IBM, August 1991)
# http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Docs/riffmci.pdf
#
# [6] Multimedia Data Standards Update
# (Microsoft, April 1994)
# http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/Docs/RIFFNEW.pdf
#
# [7] Exiftool - Riff Info Tags
# (ExifTool website)
# https://exiftool.org/TagNames/RIFF.html#Info
#
# [8] Exchangeable image file format for digital still cameras, Exif Version
# 2.32
# (Camera & Imaging Products Association, May 2019)
# http://www.cipa.jp/std/documents/e/DC-X008-Translation-2019-E.pdf
#
# [9] Audio Interchange File Format: "AIFF", Version 1.3
# (Apple, January 1989)
# http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AIFF/Docs/AIFF-1.3.pdf
#
# [10] AVI RIFF File Reference
# (Microsoft Dev Center, May 2018)
# https://docs.microsoft.com/en-us/windows/win32/directshow/avi-riff-file-reference
#
# }}}
# {{{ Common
type
RiffPrimitives* = char |
int8 | int16 | int32 | int64 |
uint | uint8 | uint16 | uint32 | uint64 |
float32 | float64
const
FourCCSize* = 4
ChunkHeaderSize* = 8
MinListChunkSize = 4
ChunkSizePlaceholder = 0xffffffff'u32
const # Top level chunk IDs
FourCC_RIFF* = "RIFF" ## RIFF chunk (little endian), may contain subchunks
FourCC_RIFX* = "RIFX" ## RIFX chunk (big endian), may contain subchunks
const # RIFF form types
FourCC_ACON* = "ACON" ## Windows NT Animated Cursor
FourCC_AVI* = "AVI " ## Audio Vide Interleave
FourCC_BND* = "BND " ## Bundle File Format (file contains a series of
## RIFF chunks)
FourCC_DIB* = "DIB " ## Device Independent Bitmap File Format
FourCC_RDIB = "RDIB" ## RIFF DIB File Format
FourCC_MIDI* = "MIDI" ## Musical Instrument Digital Interface File Format
FourCC_RMID* = "RMID" ## RIFF MIDI File Format
FourCC_PAL* = "PAL " ## Palette File Format
FourCC_RTF* = "RTF " ## Rich Text Format
FourCC_WAVE* = "WAVE" ## Waveform Audio File Format
let riffFormTypeNames* = {
FourCC_ACON: "Windows NT Animated Cursor Format",
FourCC_AVI: "Audio Vide Interleave Format",
FourCC_BND: "Bundle File Format Format",
FourCC_DIB: "Device Independent Bitmap File Format",
FourCC_RDIB: "RIFF DIB File Format",
FourCC_MIDI: "Musical Instrument Digital Interface File Format",
FourCC_RMID: "RIFF MIDI File Format",
FourCC_PAL: "Palette File Format",
FourCC_RTF: "Rich Text Format",
FourCC_WAVE: "Waveform Audio File Format"
}.toTable
const # Standard RIFF chunks
FourCC_LIST* = "LIST" ## LIST chunk, may contain subchunks
FourCC_DISP* = "DISP" ## display chunk, contains easy to representation of
## the data
FourCC_JUNK* = "JUNK" ## represents padding, filler or no relevant data
FourCC_PAD* = "PAD " ## represents padding, filler or no relevant data (if
## the pad chunk makes the next chunk align on a 2k
## boundary, this padding must be preserved when
## modifying the file)
FourCC_INFO* = "INFO" ## metadata about the file
FourCC_CSET* = "CSET" ## defines the character-set and language
## used in the file (Latin-1 is assumed if not
## specified)
FourCC_CTOC* = "CTOC" ## compound file table of contents (unsupported)
FourCC_CGRP* = "CGRP" ## compound file element group (unsupported)
# {{{ INFO subchunk types
const
# From [5]
FourCC_INFO_IARL* = "IARL"
FourCC_INFO_IART* = "IART"
FourCC_INFO_ICMS* = "ICMS"
FourCC_INFO_ICMT* = "ICMT"
FourCC_INFO_ICOP* = "ICOP"
FourCC_INFO_ICRD* = "ICRD"
FourCC_INFO_ICRP* = "ICRP"
FourCC_INFO_IDIM* = "IDIM"
FourCC_INFO_IDPI* = "IDPI"
FourCC_INFO_IENG* = "IENG"
FourCC_INFO_IGNR* = "IGNR"
FourCC_INFO_IKEY* = "IKEY"
FourCC_INFO_ILGT* = "ILGT"
FourCC_INFO_IMED* = "IMED"
FourCC_INFO_INAM* = "INAM"
FourCC_INFO_IPLT* = "IPLT"
FourCC_INFO_IPRD* = "IPRD"
FourCC_INFO_ISBJ* = "ISBJ"
FourCC_INFO_ISFT* = "ISFT"
FourCC_INFO_ISHP* = "ISHP"
FourCC_INFO_ISRC* = "ISRC"
FourCC_INFO_ISRF* = "ISRF"
FourCC_INFO_ITCH* = "ITCH"
# From [7]
FourCC_INFO_AGES* = "AGES"
FourCC_INFO_CMNT* = "CMNT"
FourCC_INFO_CODE* = "CODE"
FourCC_INFO_COMM* = "COMM"
FourCC_INFO_DIRC* = "DIRC"
FourCC_INFO_DISP* = "DISP"
FourCC_INFO_DTIM* = "DTIM"
FourCC_INFO_GENR* = "GENR"
FourCC_INFO_IAS1* = "IAS1"
FourCC_INFO_IAS2* = "IAS2"
FourCC_INFO_IAS3* = "IAS3"
FourCC_INFO_IAS4* = "IAS4"
FourCC_INFO_IAS5* = "IAS5"
FourCC_INFO_IAS6* = "IAS6"
FourCC_INFO_IAS7* = "IAS7"
FourCC_INFO_IAS8* = "IAS8"
FourCC_INFO_IAS9* = "IAS9"
FourCC_INFO_IBSU* = "IBSU"
FourCC_INFO_ICAS* = "ICAS"
FourCC_INFO_ICDS* = "ICDS"
FourCC_INFO_ICNM* = "ICNM"
FourCC_INFO_ICNT* = "ICNT"
FourCC_INFO_IDIT* = "IDIT"
FourCC_INFO_IDST* = "IDST"
FourCC_INFO_IEDT* = "IEDT"
FourCC_INFO_IENC* = "IENC"
FourCC_INFO_ILGU* = "ILGU"
FourCC_INFO_ILIU* = "ILIU"
FourCC_INFO_ILNG* = "ILNG"
FourCC_INFO_IMBI* = "IMBI"
FourCC_INFO_IMBU* = "IMBU"
FourCC_INFO_IMIT* = "IMIT"
FourCC_INFO_IMIU* = "IMIU"
FourCC_INFO_IMUS* = "IMUS"
FourCC_INFO_IPDS* = "IPDS"
FourCC_INFO_IPRO* = "IPRO"
FourCC_INFO_IRIP* = "IRIP"
FourCC_INFO_IRTD* = "IRTD"
FourCC_INFO_ISGN* = "ISGN"
FourCC_INFO_ISMP* = "ISMP"
FourCC_INFO_ISTD* = "ISTD"
FourCC_INFO_ISTR* = "ISTR"
FourCC_INFO_IWMU* = "IWMU"
FourCC_INFO_IWRI* = "IWRI"
FourCC_INFO_LANG* = "LANG"
FourCC_INFO_LOCA* = "LOCA"
FourCC_INFO_PRT1* = "PRT1"
FourCC_INFO_PRT2* = "PRT2"
FourCC_INFO_RATE* = "RATE"
FourCC_INFO_STAR* = "STAR"
FourCC_INFO_STAT* = "STAT"
FourCC_INFO_TAPE* = "TAPE"
FourCC_INFO_TCDO* = "TCDO"
FourCC_INFO_TCOD* = "TCOD"
FourCC_INFO_TITL* = "TITL"
FourCC_INFO_TLEN* = "TLEN"
FourCC_INFO_TORG* = "TORG"
FourCC_INFO_TRCK* = "TRCK"
FourCC_INFO_TURL* = "TURL"
FourCC_INFO_TVER* = "TVER"
FourCC_INFO_VMAJ* = "VMAJ"
FourCC_INFO_VMIN* = "VMIN"
FourCC_INFO_YEAR* = "YEAR"
let infoSubchunkNames* = {
# From [5]
FourCC_INFO_IARL: "Archival Location",
FourCC_INFO_IART: "Artist",
FourCC_INFO_ICMS: "Commissioned",
FourCC_INFO_ICMT: "Comments",
FourCC_INFO_ICOP: "Copyright",
FourCC_INFO_ICRD: "Creation Date",
FourCC_INFO_ICRP: "Cropped",
FourCC_INFO_IDIM: "Dimensions",
FourCC_INFO_IDPI: "Dots Per Inch",
FourCC_INFO_IENG: "Engineer",
FourCC_INFO_IGNR: "Genre",
FourCC_INFO_IKEY: "Keywords",
FourCC_INFO_ILGT: "Lightness",
FourCC_INFO_IMED: "Medium",
FourCC_INFO_INAM: "Name",
FourCC_INFO_IPLT: "Palette Setting",
FourCC_INFO_IPRD: "Product",
FourCC_INFO_ISBJ: "Subject",
FourCC_INFO_ISFT: "Software",
FourCC_INFO_ISHP: "Sharpness",
FourCC_INFO_ISRC: "Source",
FourCC_INFO_ISRF: "Source Form",
FourCC_INFO_ITCH: "Technician",
# From [7]
FourCC_INFO_AGES: "Rated",
FourCC_INFO_CMNT: "Comment",
FourCC_INFO_CODE: "Encoded By",
FourCC_INFO_COMM: "Comments",
FourCC_INFO_DIRC: "Directory",
FourCC_INFO_DISP: "Sound Scheme Title",
FourCC_INFO_DTIM: "Date Time Original",
FourCC_INFO_GENR: "Genre",
FourCC_INFO_IAS1: "First Language",
FourCC_INFO_IAS2: "Second Language",
FourCC_INFO_IAS3: "Third Language",
FourCC_INFO_IAS4: "Fourth Language",
FourCC_INFO_IAS5: "Fifth Language",
FourCC_INFO_IAS6: "Sixth Language",
FourCC_INFO_IAS7: "Seventh Language",
FourCC_INFO_IAS8: "Eighth Language",
FourCC_INFO_IAS9: "Ninth Language",
FourCC_INFO_IBSU: "Base URL",
FourCC_INFO_ICAS: "Default Audio Stream",
FourCC_INFO_ICDS: "Costume Designer",
FourCC_INFO_ICMS: "Commissioned",
FourCC_INFO_ICMT: "Comment",
FourCC_INFO_ICNM: "Cinematographer",
FourCC_INFO_ICNT: "Country",
FourCC_INFO_IDIT: "Date Time Original",
FourCC_INFO_IDST: "Distributed By",
FourCC_INFO_IEDT: "Edited By",
FourCC_INFO_IENC: "Encoded By",
FourCC_INFO_ILGU: "Logo URL",
FourCC_INFO_ILIU: "Logo Icon URL",
FourCC_INFO_ILNG: "Language",
FourCC_INFO_IMBI: "More Info Banner Image",
FourCC_INFO_IMBU: "More Info Banner URL",
FourCC_INFO_IMIT: "More Info Text",
FourCC_INFO_IMIU: "More Info URL",
FourCC_INFO_IMUS: "Music By",
FourCC_INFO_IPDS: "Production Designer",
FourCC_INFO_IPRO: "Produced By",
FourCC_INFO_IRIP: "Ripped By",
FourCC_INFO_IRTD: "Rating",
FourCC_INFO_ISGN: "Secondary Genre",
FourCC_INFO_ISMP: "Time Code",
FourCC_INFO_ISTD: "Production Studio",
FourCC_INFO_ISTR: "Starring",
FourCC_INFO_IWMU: "Watermark URL",
FourCC_INFO_IWRI: "Written By",
FourCC_INFO_LANG: "Language",
FourCC_INFO_LOCA: "Location",
FourCC_INFO_PRT1: "Part",
FourCC_INFO_PRT2: "Number Of Parts",
FourCC_INFO_RATE: "Rate",
FourCC_INFO_STAR: "Starring",
FourCC_INFO_STAT: "Statistics",
FourCC_INFO_TAPE: "Tape Name",
FourCC_INFO_TCDO: "End Timecode",
FourCC_INFO_TCOD: "Start Timecode",
FourCC_INFO_TITL: "Title",
FourCC_INFO_TLEN: "Length (ms)",
FourCC_INFO_TORG: "Organization",
FourCC_INFO_TRCK: "Track Number",
FourCC_INFO_TURL: "URL",
FourCC_INFO_TVER: "Version",
FourCC_INFO_VMAJ: "Vegas Version Major",
FourCC_INFO_VMIN: "Vegas Version Minor",
FourCC_INFO_YEAR: "Year"
}.toTable
# }}}
type
ChunkKind* = enum
ckChunk, ckGroup
ChunkInfo* = object
## contains information about a chunk
id*: string ## 4-char chunk ID (FourCC)
size*: uint32 ## chunk data length in bytes (NOT including the
## optional pad byte if data length is odd)
filePos*: int64 ## absolute position in bytes from the start of the file
case kind*: ChunkKind ## ckGroup - group chunks,
## ckChunk - normal subchunks
of ckGroup: formatTypeId*: string ## format type FourCC for group chunks
of ckChunk: discard
Cursor* = object ## a location in the RIFF file (a chunk path plus a chunk offset)
path*: seq[ChunkInfo]
chunkPos*: uint32
filePos*: int64
func validFourCC*(fourCC: string, relaxed: bool = false): bool =
## Returns true is the passed in FourCC is valid. A FourCC is valid if:
## * it is 4 ASCII characters long
## * it only contains alphanumeric ASCII characters or spaces
## * spaces are only allowed in trailing position
##
## If the `relaxed` flag is set to true, all ASCII characters are allowed
## (but the trailing spaces only rule still applies).
##
if fourCC.len != 4: return false
var spaceFound = false
for c in fourCC:
if spaceFound:
if c != ' ': return false
elif c == ' ': spaceFound = true
elif not relaxed and not c.isAlphaNumeric: return false
return true
func fourCCToCharStr*(fourCC: string): string =
## Converts a FourCC to a printable string.
##
## ```
## fourCCToCharStr("RIFF") # returns "('R', 'I', 'F', 'F')"
## fourCCToCharStr("A#\27 ") # returns "('A', '#', '\\27', ' ')"
## ```
result = "("
for i in 0..3:
let c = fourCC[i]
if c < ' ': result &= fmt"'\{c.ord}'"
else: result &= fmt"'{c}'"
if i < 3: result &= ", "
result &= ")"
# }}}
# {{{ Reader
type
RiffReader* = ref object ## a RIFF file opened for reading
fs: FileStream
path: seq[ChunkInfo]
currParentChunk: ChunkInfo
doCheckChunkLimits: bool
doCheckNotInGroup: bool
closed: bool
RiffReadError* = object of IOError
ChunkSeekPos* = enum ## cspSet - from the start of the chunk
## cspCur - from the current position
## cspEnd - from the end of the chunk
cspSet, cspCur, cspEnd
using rr: RiffReader
func atRootChunk(rr): bool =
rr.path.len == 1
template currChunk(rr): ChunkInfo = rr.path[^1]
func parentChunk(rr): ChunkInfo =
if rr.atRootChunk: rr.path[0] else: rr.path[^2]
proc cursorPop(rr): ChunkInfo =
result = rr.path.pop
rr.currParentChunk = rr.parentChunk
proc cursorAdd(rr; ci: ChunkInfo) =
rr.path.add(ci)
rr.currParentChunk = rr.parentChunk
proc checkNotClosed(rr) =
if rr.closed:
raise newException(RiffReadError, "Reader has been closed")
type ReadOperation = enum
roReadingData = (0, "Reading data"),
roSetChunkPos = (1, "Setting chunk position")
proc checkNotInGroupChunk(rr; op: ReadOperation) =
if rr.doCheckNotInGroup:
if rr.currChunk.kind == ckGroup:
raise newException(RiffReadError,
fmt"{op} is not allowed in a group chunk")
proc filename*(rr): string =
## Returns the filename of the RIFF file.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
rr.checkNotClosed
rr.fs.filename
func endian*(rr): Endianness =
## Returns the endianness of the RIFF file.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
rr.checkNotClosed
rr.fs.endian
func formTypeId*(rr): string =
## Returns the form type ID of the RIFF file (this indicates the concrete
## format of the file, e.g. "WAVE" or "AVI ").
## Raises a `RiffReadError` if the reader is closed or not initialised.
rr.checkNotClosed
rr.path[0].formatTypeId
proc currentChunk*(rr): ChunkInfo =
## Returns information about the current chunk.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
rr.checkNotClosed
rr.currChunk
proc checkChunkLimits(rr: RiffReader, numBytes: Natural) {.inline.} =
if not rr.doCheckChunkLimits: return
let
pc = rr.currParentChunk
chunkPos = rr.fs.getPosition - (pc.filePos + ChunkHeaderSize)
if chunkPos + numBytes > pc.size.int64:
raise newException(RiffReadError,
"Cannot read past the end of the current group chunk, " &
fmt"chunk size: {pc.size}, chunk pos: {chunkPos}, " &
fmt"bytes to read: {numBytes}")
proc getChunkPos*(rr): uint32 =
## Returns the current chunk position. The start of the chunk data
## (the first byte after the chunk headers) is the zero position.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
result = (rr.fs.getPosition - rr.currChunk.filePos - ChunkHeaderSize).uint32
if rr.currChunk.kind == ckGroup:
dec(result, FourCCSize)
proc setChunkPos*(rr; pos: int64, relativeTo: ChunkSeekPos = cspSet) =
## Sets the current chunk position according to the `relativeTo` parameter.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
let ci = rr.currChunk
let currChunkPos = rr.getChunkPos.int64
var newPos = case relativeTo
of cspSet: pos
of cspCur: currChunkPos + pos
of cspEnd: ci.size.int64 + pos
if newPos < 0 or newPos >= ci.size.int64:
raise newException(RiffReadError,
"Cannot seek past the bounds of the current chunk, " &
fmt"chunk size: {ci.size}, current chunk pos: {currChunkPos}, " &
fmt"new chunk pos: {newPos}")
rr.fs.setPosition(ci.filePos + ChunkHeaderSize + newPos)
proc getFilePos*(rr): int64 =
## Returns the current absolute file position.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.fs.getPosition
proc cursor*(rr): Cursor =
## Returns a cursor that points the current chunk and chunk offset.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
Cursor(
path: deepCopy(rr.path),
filePos: rr.fs.getPosition,
chunkPos: rr.getChunkPos
)
proc `cursor=`*(rr; c: Cursor) =
## Restores the current chunk and chunk offset from a cursor.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.path = deepCopy(c.path)
rr.currParentChunk = rr.parentChunk
rr.fs.setPosition(c.filePos)
proc read*(rr; T: typedesc[RiffPrimitives]): T =
## Reads a numeric value; the type needs to be passed in as an argument.
##
## ```
## let i8 = r.read(uint8)
## let f32 = r.read(float32)
## let i64 = r.read(int64)
## ```
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.checkNotInGroupChunk(roReadingData)
let numBytes = sizeof(T)
checkChunkLimits(rr, numBytes)
result = rr.fs.read(T)
proc read*[T: RiffPrimitives](rr; buf: var openArray[T],
startIndex, numValues: Natural) =
## Reads `numValues` number of values into `buf` starting from `startIndex`.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.checkNotInGroupChunk(roReadingData)
let numBytes = numValues * sizeof(T)
checkChunkLimits(rr, numBytes)
rr.fs.read(buf, startIndex, numValues)
proc readChar*(rr): char =
## Reads a char.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.checkNotInGroupChunk(roReadingData)
checkChunkLimits(rr, 1)
result = rr.fs.read(char)
proc readStr*(rr; length: Natural): string =
## Reads `length` number of bytes as an UTF-8 string.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
rr.checkNotInGroupChunk(roReadingData)
checkChunkLimits(rr, length)
result = rr.fs.readStr(length)
proc readBStr*(rr): string =
## Reads a Pascal-style string (one `length` leading byte followed by
## `length` bytes of character data).
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
let length = rr.read(uint8)
result = rr.readStr(length)
proc readWStr*(rr): string =
## Reads a Pascal-style string (one `length` leading word (16-bit int)
## followed by `length` bytes of character data).
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
let length = rr.read(uint16)
result = rr.readStr(length)
proc readZStr*(rr): string =
## Read a C-style null-terminated string.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
result = ""
while true:
let c = rr.read(char)
if c == chr(0): return
result &= c
proc readBZStr*(rr): string =
## Reads a Pascal-style string (one `length` leading byte followed by
## `length` bytes of character data), that is also null-terminated.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
result = rr.readBStr
rr.setChunkPos(1, cspCur)
proc readWZStr*(rr): string =
## Reads a Pascal-style string (one `length` leading word (16-bit int)
## followed by `length` bytes of character data), that is also
## null-terminated.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
result = rr.readWStr
rr.setChunkPos(1, cspCur)
proc readFourCC*(rr): string =
## Reads the next 4-bytes as a FourCC string. It does not validate the
## FourCC.
##
## Raises a `RiffReadError` if the reader is closed or not initialised, or
## if an attempt has been made to read past the end of the chunk.
##
## Raises an `IOError` on read errors.
rr.readStr(4)
func padToEven(n: SomeInteger): SomeInteger =
if n mod 2 == 1: n+1 else: n
proc hasNextChunk*(rr): bool =
## Returns true if there are more sibling subchunks under the current parent
## group chunk.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
rr.checkNotClosed
let
pc = rr.parentChunk
cc = rr.currChunk
parentEndPos = pc.filePos + ChunkHeaderSize + pc.size.int64
currEndPos = cc.filePos + ChunkHeaderSize + padToEven(cc.size.int64)
return currEndPos < parentEndPos
proc hasSubchunks*(rr): bool =
return rr.currChunk.kind == ckGroup and
rr.currChunk.size.int > MinListChunkSize
proc readChunk(rr; nextPos: int64): ChunkInfo =
try:
rr.doCheckNotInGroup = false
let chunkId = rr.readFourCC
if not validFourCC(chunkId):
raise newException(RiffReadError,
fmt"Invalid chunk ID: {fourCCToCharStr(chunkId)}")
var ci = if chunkId == FourCC_LIST:
ChunkInfo(kind: ckGroup)
else:
ChunkInfo(kind: ckChunk)
ci.id = chunkId
ci.size = rr.read(uint32)
# TODO check against filesize & remaining filesize
ci.filePos = nextPos
if ci.kind == ckGroup:
ci.formatTypeId = rr.readFourCC
if not validFourCC(ci.formatTypeId):
raise newException(RiffReadError,
fmt"Invalid format type ID: {fourCCToCharStr(ci.formatTypeId)}")
result = ci
except: raise
finally:
rr.doCheckNotInGroup = true
proc nextChunk*(rr): ChunkInfo =
## Moves the current chunk pointer to the next sibling subchunk of the
## current parent group chunk, and sets the chunk offset to zero.
##
## Raises a `RiffReadError` if we're at the last subchunk of the current
## group chunk, or if an invalid FourCC has been encountered, or if the
## reader is closed or not initialised.
##
## Raises an `IOError` on read errors.
rr.checkNotClosed
if not rr.hasNextChunk:
raise newException(RiffReadError,
"Cannot go to next chunk: " &
"there are no more subchunks in the current group chunk")
let cc = rr.currChunk
let nextPos = cc.filePos + ChunkHeaderSize + padToEven(cc.size.int64)
rr.fs.setPosition(nextPos)
let ci = rr.readChunk(nextPos)
discard rr.cursorPop
rr.cursorAdd(ci)
result = ci
proc enterGroup*(rr): ChunkInfo =
##
## Raises a `RiffReadError` if the current chunk is not a group chunk, or if
## the reader is closed or not initialised.
rr.checkNotClosed
if not rr.hasSubchunks:
raise newException(RiffReadError,
"Cannot enter group chunk: current chunk is not a group chunk, " &
fmt"chunkId: {fourCCToCharStr(rr.currChunk.id)}")
elif not rr.hasSubchunks:
raise newException(RiffReadError,
"Cannot enter group chunk: " &
"there are no more subchunks in the current group chunk")
let nextPos = rr.currChunk.filePos + ChunkHeaderSize + FourCCSize
rr.fs.setPosition(nextPos)
let ci = rr.readChunk(nextPos)
rr.cursorAdd(ci)
result = ci
proc exitGroup*(rr) =
## Sets the current chunk to the parent group chunk.
##
## Raises a `RiffReadError` if we're at the root level RIFF group chunk, or
## if the reader is closed or not initialised.
rr.checkNotClosed
if rr.atRootChunk:
raise newException(RiffReadError, "Cannot exit root chunk")
elif rr.parentChunk.kind == ckGroup:
discard rr.cursorPop
else:
# This error indicates a bug, it should never happen
raise newException(RiffReadError,
fmt"Cannot exit non-group chunk '{rr.currChunk.id}'")
# TODO ignore/allow lists
iterator walkChunks*(rr): ChunkInfo {.closure.} =
let startCur = rr.cursor
let startDepth = rr.path.len
var ci = rr.currentChunk
yield ci
if ci.kind == ckChunk or
ci.kind == ckGroup and rr.hasSubchunks:
block main:
while true:
if ci.kind == ckGroup and rr.hasSubchunks:
ci = rr.enterGroup
yield ci
else:
block next:
if rr.hasNextChunk:
ci = rr.nextChunk
yield ci
else:
if rr.path.len == startDepth: break main
else:
rr.exitGroup
if rr.path.len == startDepth: break main
break next
rr.cursor = startCur
proc readFormChunkHeader(rr): ChunkInfo =
var ci = ChunkInfo(kind: ckGroup)
ci.id = rr.readFourCC
case ci.id:
of FourCC_RIFF: rr.fs.endian = littleEndian
of FourCC_RIFX: rr.fs.endian = bigEndian
else:
raise newException(RiffReadError,
fmt"Unknown root chunk ID: {fourCCToCharStr(ci.id)}")
ci.size = rr.read(uint32)
# TODO check against filesize
ci.filePos = 0
ci.formatTypeId = rr.readFourCC
if not validFourCC(ci.formatTypeId):
raise newException(RiffReadError,
fmt"Invalid format type ID: {fourCCToCharStr(ci.formatTypeId)}")
result = ci
proc init(rr) =
rr.doCheckChunkLimits = false
let ci = rr.readFormChunkHeader
rr.path = newSeq[ChunkInfo]()
rr.cursorAdd(ci)
rr.doCheckChunkLimits = true
rr.doCheckNotInGroup = true
proc openRiffFile*(filename: string, bufSize: int = -1): RiffReader =
## Opens a RIFF file specified by `filename`. Optionally overrides the
## default `bufSize` of the underlying binary stream reader. The endianness
## of the file is determined from the RIFF headers.
##
## Raises a `RiffReadError` if the file is not a valid RIFF file.
##
## Raises an `IOError` if the file cannot be opened.
var rr = new RiffReader
rr.fs = openFileStream(filename, littleEndian, fmRead, bufSize)
rr.init
result = rr
proc openRiffFile*(f: File, bufSize: int = -1): RiffReader =
## Opens a RIFF file from an existing file handle. Optionally overrides the
## default `bufSize` of the underlying binary stream reader. The endianness
## of the file is determined from the RIFF headers.
##
## Raises a `RiffReadError` if the file is not a valid RIFF file.
##
## Raises an `IOError` if the file cannot be opened.
var rr = new RiffReader
rr.fs = newFileStream(f, littleEndian)
rr.init
result = rr
proc close*(rr) =
## Closes the RIFF file.
##
## Raises a `RiffReadError` if the reader is closed or not initialised.
##
## Raises an `IOError` if the file cannot be closed.
rr.checkNotClosed
rr.fs.close
rr.fs = nil
rr.closed = true
# }}}
# {{{ Writer
type
RiffWriter* = ref object
fs: FileStream
path: seq[ChunkInfo]
trackChunkSize: bool
inGroupChunk: bool
closed: bool
RiffWriteError* = object of IOError
using rw: RiffWriter
proc checkNotClosed(rw) =
if rw.closed:
raise newException(RiffWriteError, "Writer has been closed")
proc filename*(rw): string =
## Returns the name of the file associated with the reader. If the
## reader was initialised from a file handle, the filename will be an
## empty string.
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
rw.checkNotClosed
rw.fs.filename
proc endian*(rw): Endianness =
## Returns the endianness of the RIFF file associated with the reader.
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
rw.checkNotClosed
rw.fs.endian
proc incChunkSize(rw; numBytes: Natural) =
if rw.trackChunkSize:
inc(rw.path[^1].size, numBytes)
proc write*[T: RiffPrimitives](rw; value: T) =
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
checkNotClosed(rw)
rw.fs.write(value)
incChunkSize(rw, sizeof(T))
proc write*[T: RiffPrimitives](rw; buf: var openArray[T],
startIndex, numValues: Natural) =
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
checkNotClosed(rw)
rw.fs.write(buf, startIndex, numValues)
incChunkSize(rw, numValues * sizeof(T))
proc writeChar*(rw; c: char) =
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
checkNotClosed(rw)
rw.fs.write(c)
incChunkSize(rw, 1)
proc writeStr*(rw; s: string) =
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
checkNotClosed(rw)
rw.fs.writeStr(s)
incChunkSize(rw, s.len)
proc writeBStr*(rw; s: string) =
let length = min(s.len, uint8.high.int).uint8
rw.write(length)
var ss = s
setLen(ss, length)
rw.writeStr(ss)
proc writeWStr*(rw; s: string) =
let length = min(s.len, uint16.high.int).uint16
rw.write(length)
var ss = s
setLen(ss, length)
rw.writeStr(ss)
proc writeZStr*(rw; s: string) =
rw.writeStr(s)
rw.write(0'u8)
proc writeBZStr*(rw; s: string) =
rw.writeBStr(s)
rw.write(0'u8)
proc writeWZStr*(rw; s: string) =
rw.writeWStr(s)
rw.write(0'u8)
proc writeFourCC*(rw; fourCC: string) =
##
## Raises a `RiffReadError` if the writer is closed or not initialised.
assert fourCC.len == 4
checkNotClosed(rw)