Iso encoding specs

This section uses terminology from Web IDL. Browser user agents must support this API. JavaScript implementations should support this API. Other user agents or programming languages are encouraged to use an API suitable to their needs, which might not be this one. The following example uses the TextEncoder object to encode an array of strings into an ArrayBuffer. The result is a Uint8Array containing the number of strings as a Uint32Array , followed by the length of the first string as a Uint32Array , the UTF-8 encoded string data, the length of the second string as a Uint32Array , the string data, and so on.

The following example decodes an ArrayBuffer containing data encoded in the format produced by the previous example, or an equivalent algorithm for encodings other than UTF-8 , back into an array of strings. These objects have an associated:. Let item be the result of reading from ioQueue. If item is end-of-queue , then return output. This algorithm is intentionally different with respect to BOM handling from the decode algorithm used by the rest of the platform to give API users more control.

A TextDecoder object has an associated do not flush , which is a boolean, initially false. Returns a new TextDecoder object. If label is either not a label or is a label for replacement , throws a RangeError. Returns true if error mode is " fatal ", otherwise false.

Returns the value of ignore BOM. The new TextDecoder label , options constructor steps are:. Let encoding be the result of getting an encoding from label. If encoding is failure or replacement , then throw a RangeError. The decode input , options method steps are:.

Implementations are strongly encouraged to use an implementation strategy that avoids this copy. When doing so they will have to make sure that changes to input do not affect future calls to decode.

The memory exposed by SharedArrayBuffer objects does not adhere to data race freedom properties required by the memory model of programming languages typically used for implementations.

When implementing, take care to use the appropriate facilities when accessing memory exposed by SharedArrayBuffer objects. Otherwise, if result is error , throw a TypeError. The encoding getter steps are to return " utf-8 ". It also offers no stream option as no encoder requires buffering of scalar values.

Returns a new TextEncoder object. Runs the UTF-8 encoder on source , stores the result of that operation into destination , and returns the progress made as an object wherein read is the number of converted code units of source and written is the number of bytes modified in destination. The new TextEncoder constructor steps are to do nothing. The encode input method steps are:. Let item be the result of reading from input. Let result be the result of processing an item with item , an instance of the UTF-8 encoder , input , output , and " fatal ".

Assert: result is not an error. The UTF-8 encoder cannot return error. If result is finished , then convert output into a byte sequence and return a Uint8Array object wrapping an ArrayBuffer containing output. The encodeInto source , destination method steps are:. Let encoder be an instance of the UTF-8 encoder. The handler algorithm invoked below requires this argument, but it is not used by the UTF-8 encoder. Let item be the result of reading from source. If result is finished , then break.

Write the bytes in result into destination , with startingOffset set to written. See the warning for SharedArrayBuffer objects above. Otherwise, break. The encodeInto method can be used to encode a string into an existing ArrayBuffer object. Various details below are left as an exercise for the reader, but this demonstrates an approach one could take to use this method:.

Returns a new TextDecoderStream object. Returns true if error mode is " fatal ", and false otherwise. Typically this will be used via the pipeThrough method on a ReadableStream source. The new TextDecoderStream label , options constructor steps are:. Let transformAlgorithm be an algorithm which takes a chunk argument and runs the decode and enqueue a chunk algorithm with this and chunk. Let flushAlgorithm be an algorithm which takes no arguments and runs the flush and enqueue algorithm with this.

Let transformStream be a new TransformStream. Set up transformStream with transformAlgorithm set to transformAlgorithm and flushAlgorithm set to flushAlgorithm. The decode and enqueue a chunk algorithm, given a TextDecoderStream object decoder and a chunk , runs these steps:. If item is end-of-queue , then:. If result is error , then throw a TypeError. The flush and enqueue algorithm, which handles the end of data from the input ReadableStream object, given a TextDecoderStream object decoder , runs these steps:.

If result is finished , then:. A TextEncoderStream object has an associated:. Returns a new TextEncoderStream object. The new TextEncoderStream constructor steps are:. Let transformAlgorithm be an algorithm which takes a chunk argument and runs the encode and enqueue a chunk algorithm with this and chunk. Let flushAlgorithm be an algorithm which runs the encode and flush algorithm with this.

The encode and enqueue a chunk algorithm, given a TextEncoderStream object encoder and chunk , runs these steps:. Let input be the result of converting chunk to a DOMString. The behavior is otherwise identical to USVString.

Convert output into a byte sequence. Let chunk be a Uint8Array object wrapping an ArrayBuffer containing output. Let result be the result of executing the convert code unit to scalar value algorithm with encoder , item and input. Prepend item to input. This is equivalent to the " convert a string into a scalar value string " algorithm from the Infra Standard, but allows for surrogate pairs that are split between strings. The encode and flush algorithm, given a TextEncoderStream object encoder , runs these steps:.

A byte order mark has priority over a label as it has been found to be more accurate in deployed content. If byte is end-of-queue , return finished.

If UTF-8 bytes needed is 0, based on byte :. Set UTF-8 bytes needed to 1. Set UTF-8 bytes needed to 2. If byte is 0xF0, set UTF-8 lower boundary to 0x Set UTF-8 bytes needed to 3.

Prepend byte to ioQueue. Shift the existing bits of UTF-8 code point left by six places and set the newly-vacated six least significant bits to the six least significant bits of byte. Increase UTF-8 bytes seen by one. Let code point be UTF-8 code point.

No other behavior is permitted per the Encoding Standard other algorithms that achieve the same result are fine, even encouraged. If code point is end-of-queue , return finished. This algorithm has identical results to the one described in the Unicode standard. It is included here for completeness. An encoding where each byte is either a single code point or nothing, is a single-byte encoding.

Single-byte encodings share the decoder and encoder. Read more about certification and how to find a certification body. Browse or search our catalogue Search. ISO standards are internationally agreed by experts Think of them as a formula that describes the best way of doing something. For instance, Quality management standards to help work more efficiently and reduce product failures. Environmental management standards to help reduce environmental impacts, reduce waste and be more sustainable.

Health and safety standards to help reduce accidents in the workplace. Energy management standards to help cut energy consumption. Food safety standards to help prevent food from being contaminated. The format of the volume descriptors is as follows:. When starting out with a basic CD, we are going to be interested in the Primary Volume Descriptor, which points us to the root directory and path tables, which both allow us to find any file on the CD. Using the path table is ideal for minimal implementations which do not wish to search the directory hierarchy node by node.

This is slower string comparisons across the entire file system but easier to implement. It records at bytes 71 to 74 as little-endian bit number the block address of the El Torito Boot Catalog.

This catalog lists the available boot images, which serve as starting points of booting systems. This is a lengthy descriptor, but it contains some very useful information for reading the rest of the file system.

This means that the only fields in use for the volume set terminator are the type code , the standard identifier 'CD' and the descriptor version 0x The Path Table contains a well-ordered sequence of records describing every directory extent on the CD.

There are some exceptions with this: the Path Table can only contain records, due to the length of the "Parent Directory Number" field. If there are more than this number of directories on the disc, some CD authoring software will ignore this limit and create a non-compliant CD this applies to some earlier versions of Nero, for example.

If your file system uses the path table, you should be aware of this possibility. Windows uses the Path Table and will fail with such non-compliant CD's additional nodes exist but appear as zero-byte. Linux, which uses the directory tables is not affected by this issue. The location of the path tables can be found in the Primary Volume Descriptor.

There are two table types - the L-Path table relevant to x86 and the M-Path table. The path table is in ascending order of directory level and is alphabetically sorted within each directory level. At some point when reading from an ISO CD, you will need a directory record to locate a file, even if you generally use the path table to locate the directory initially. Unlike the path tables, there is only one version of each directory table, and multi byte numbers are in both-endian format.

Every directory will start with 2 special entries: an empty string, describing the ". A directory record is laid out as follows:. System Use - The remaining bytes up to the maximum record size of may be used for extensions of ISO Even if a directory spans multiple sectors, the directory entries are not permitted to cross the sector boundary unlike the path table.

Where there is not enough space to record an entire directory entry at the end of a sector, that sector is zero-padded and the next consecutive sector is used. Some of the above fields need explanation. This is quite a contrast to the PVD which contains ASCII encoded decimal values, but this format is presumably used to save disc space over a large number of entries. The other field that needs some explanation is the File Flags field. This is represented by one bit flags as follows:. By now, you should be able to see that there are two main ways to navigate to a file record.

You an either search the path table, or you can search the full directory structure. You may find it more convenient and faster to cache the path table, loading directories only when necessary.

If you are using the Path Table method, you will still need to know about Directory Records to find the file you are looking for. Basically, you search the path in a reverse order, following the "Parent Directory" links in the Path Table. Once you have located the directory containing the file you want, load that Directory and scan it for the appropriate file name. Alternatively, you can ignore the Path Table and just cache the root directory from the Primary Volume Descriptor.

You then load each directory in turn. Both can be combined in the same filesystem. ISO and Rock Ridge will show the same tree of files but with different names. Joliet can show a completely different tree than ISO.