diff options
Diffstat (limited to 'vendor/github.com/gdamore/tcell/encoding.go')
| -rw-r--r-- | vendor/github.com/gdamore/tcell/encoding.go | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/vendor/github.com/gdamore/tcell/encoding.go b/vendor/github.com/gdamore/tcell/encoding.go new file mode 100644 index 0000000..596a6e8 --- /dev/null +++ b/vendor/github.com/gdamore/tcell/encoding.go @@ -0,0 +1,139 @@ +// Copyright 2015 The TCell Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use file except in compliance with the License. +// You may obtain a copy of the license at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package tcell + +import ( + "strings" + "sync" + + "golang.org/x/text/encoding" + + gencoding "github.com/gdamore/encoding" +) + +var encodings map[string]encoding.Encoding +var encodingLk sync.Mutex +var encodingFallback EncodingFallback = EncodingFallbackFail + +// RegisterEncoding may be called by the application to register an encoding. +// The presence of additional encodings will facilitate application usage with +// terminal environments where the I/O subsystem does not support Unicode. +// +// Windows systems use Unicode natively, and do not need any of the encoding +// subsystem when using Windows Console screens. +// +// Please see the Go documentation for golang.org/x/text/encoding -- most of +// the common ones exist already as stock variables. For example, ISO8859-15 +// can be registered using the following code: +// +// import "golang.org/x/text/encoding/charmap" +// +// ... +// RegisterEncoding("ISO8859-15", charmap.ISO8859_15) +// +// Aliases can be registered as well, for example "8859-15" could be an alias +// for "ISO8859-15". +// +// For POSIX systems, the tcell package will check the environment variables +// LC_ALL, LC_CTYPE, and LANG (in that order) to determine the character set. +// These are expected to have the following pattern: +// +// $language[.$codeset[@$variant] +// +// We extract only the $codeset part, which will usually be something like +// UTF-8 or ISO8859-15 or KOI8-R. Note that if the locale is either "POSIX" +// or "C", then we assume US-ASCII (the POSIX 'portable character set' +// and assume all other characters are somehow invalid.) +// +// Modern POSIX systems and terminal emulators may use UTF-8, and for those +// systems, this API is also unnecessary. For example, Darwin (MacOS X) and +// modern Linux running modern xterm generally will out of the box without +// any of this. Use of UTF-8 is recommended when possible, as it saves +// quite a lot processing overhead. +// +// Note that some encodings are quite large (for example GB18030 which is a +// superset of Unicode) and so the application size can be expected ot +// increase quite a bit as each encoding is added. The East Asian encodings +// have been seen to add 100-200K per encoding to the application size. +// +func RegisterEncoding(charset string, enc encoding.Encoding) { + encodingLk.Lock() + charset = strings.ToLower(charset) + encodings[charset] = enc + encodingLk.Unlock() +} + +// EncodingFallback describes how the system behavees when the locale +// requires a character set that we do not support. The system always +// supports UTF-8 and US-ASCII. On Windows consoles, UTF-16LE is also +// supported automatically. Other character sets must be added using the +// RegisterEncoding API. (A large group of nearly all of them can be +// added using the RegisterAll function in the encoding sub package.) +type EncodingFallback int + +const ( + // EncodingFallbackFail behavior causes GetEncoding to fail + // when it cannot find an encoding. + EncodingFallbackFail = iota + + // EncodingFallbackASCII behaviore causes GetEncoding to fall back + // to a 7-bit ASCII encoding, if no other encoding can be found. + EncodingFallbackASCII + + // EncodingFallbackUTF8 behavior causes GetEncoding to assume + // UTF8 can pass unmodified upon failure. Note that this behavior + // is not recommended, unless you are sure your terminal can cope + // with real UTF8 sequences. + EncodingFallbackUTF8 +) + +// SetEncodingFallback changes the behavior of GetEncoding when a suitable +// encoding is not found. The default is EncodingFallbackFail, which +// causes GetEncoding to simply return nil. +func SetEncodingFallback(fb EncodingFallback) { + encodingLk.Lock() + encodingFallback = fb + encodingLk.Unlock() +} + +// GetEncoding is used by Screen implementors who want to locate an encoding +// for the given character set name. Note that this will return nil for +// either the Unicode (UTF-8) or ASCII encodings, since we don't use +// encodings for them but instead have our own native methods. +func GetEncoding(charset string) encoding.Encoding { + charset = strings.ToLower(charset) + encodingLk.Lock() + defer encodingLk.Unlock() + if enc, ok := encodings[charset]; ok { + return enc + } + switch encodingFallback { + case EncodingFallbackASCII: + return gencoding.ASCII + case EncodingFallbackUTF8: + return encoding.Nop + } + return nil +} + +func init() { + // We always support UTF-8 and ASCII. + encodings = make(map[string]encoding.Encoding) + encodings["utf-8"] = gencoding.UTF8 + encodings["utf8"] = gencoding.UTF8 + encodings["us-ascii"] = gencoding.ASCII + encodings["ascii"] = gencoding.ASCII + encodings["iso646"] = gencoding.ASCII +} |