encoding/unicode: add UTF8BOM encoding

Some editors always add a BOM to UTF-8. Tradionally the BOM
has been used to detect byte order encoding, which is irrelevant
for UTF-8. These editors, however, use the UTF-8 BOM as
a signature, allowing to override a charmap encoding if such
a BOM is present. This is possible as the occurence of a BOM
in such encodings is highly unlikely.

This UTF8BOM encoding implements a simple encoding for this.
It is intended for applications that require a UTF-8 encoding, but
want to handle files written by such editors without explicit BOM
handling. It can also be used to create such files.

NOTE: there is currently no encoding that implements the fallback
encoding of such editors. The BOMOverride functlinality in this
package allows implementing such an encoder, with relative ease,
though.

Change-Id: I430851a1d93351bf6055eebe88005984dde451d9
Reviewed-on: https://go-review.googlesource.com/c/text/+/234277
Reviewed-by: Russ Cox <rsc@golang.org>
2 files changed
tree: 6317f8c4f3b7b5b0bc89f02b2ad1a5d259dc3bf9
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. cases/
  10. cmd/
  11. codereview.cfg
  12. collate/
  13. currency/
  14. date/
  15. doc.go
  16. encoding/
  17. feature/
  18. gen.go
  19. go.mod
  20. go.sum
  21. internal/
  22. language/
  23. message/
  24. number/
  25. runes/
  26. search/
  27. secure/
  28. transform/
  29. unicode/
  30. width/
README.md

Go Text

This repository holds supplementary Go libraries for text processing, many involving Unicode.

Semantic Versioning

This repo uses Semantic versioning (http://semver.org/), so

  1. MAJOR version when you make incompatible API changes,
  2. MINOR version when you add functionality in a backwards-compatible manner, and
  3. PATCH version when you make backwards-compatible bug fixes.

Until version 1.0.0 of x/text is reached, the minor version is considered a major version. So going from 0.1.0 to 0.2.0 is considered to be a major version bump.

A major new CLDR version is mapped to a minor version increase in x/text. Any other new CLDR version is mapped to a patch version increase in x/text.

It is important that the Unicode version used in x/text matches the one used by your Go compiler. The x/text repository supports multiple versions of Unicode and will match the version of Unicode to that of the Go compiler. At the moment this is supported for Go compilers from version 1.7.

Download/Install

The easiest way to install is to run go get -u golang.org/x/text. You can also manually git clone the repository to $GOPATH/src/golang.org/x/text.

Contribute

To submit changes to this repository, see http://golang.org/doc/contribute.html.

To generate the tables in this repository (except for the encoding tables), run go generate from this directory. By default tables are generated for the Unicode version in core and the CLDR version defined in golang.org/x/text/unicode/cldr.

Running go generate will as a side effect create a DATA subdirectory in this directory, which holds all files that are used as a source for generating the tables. This directory will also serve as a cache.

Testing

Run

go test ./...

from this directory to run all tests. Add the “-tags icu” flag to also run ICU conformance tests (if available). This requires that you have the correct ICU version installed on your system.

TODO:

  • updating unversioned source files.

Generating Tables

To generate the tables in this repository (except for the encoding tables), run go generate from this directory. By default tables are generated for the Unicode version in core and the CLDR version defined in golang.org/x/text/unicode/cldr.

Running go generate will as a side effect create a DATA subdirectory in this directory which holds all files that are used as a source for generating the tables. This directory will also serve as a cache.

Versions

To update a Unicode version run

UNICODE_VERSION=x.x.x go generate

where x.x.x must correspond to a directory in https://www.unicode.org/Public/. If this version is newer than the version in core it will also update the relevant packages there. The idna package in x/net will always be updated.

To update a CLDR version run

CLDR_VERSION=version go generate

where version must correspond to a directory in https://www.unicode.org/Public/cldr/.

Note that the code gets adapted over time to changes in the data and that backwards compatibility is not maintained. So updating to a different version may not work.

The files in DATA/{iana|icu|w3|whatwg} are currently not versioned.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the image repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/text:” in the subject line, so it is easy to find.