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52756
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1 //! Character transcoding support.
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2
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3 use core::str;
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4 use std::borrow::Cow;
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5
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6 use crate::{errors::HgError, utils::Escaped};
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7 use unicode_width::UnicodeWidthStr as _;
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8
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9 /// String encoder and decoder.
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10 #[derive(Copy, Clone, Debug)]
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11 pub struct Encoder {
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12 /// The user's local encoding.
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13 local_encoding: Encoding,
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14 /// What to do when decoding fails. (Encoding always uses
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15 /// `Mode::Replace`).
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16 decoding_mode: Mode,
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17 /// Width to use for characters that can be interpreted either as narrow
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18 /// or wide depending on the context.
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19 pub ambiguous_width: Width,
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20 }
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21
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22 /// Character encoding.
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23 #[derive(Copy, Clone, Debug)]
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24 pub enum Encoding {
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25 Utf8,
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26 Ascii,
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27 }
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28
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29 /// Character decoding mode.
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30 #[derive(Copy, Clone, Debug)]
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31 pub enum Mode {
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32 /// Produce an error message for invalid characters.
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33 Strict,
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34 /// Replace invalid characters with a special character.
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35 Replace,
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36 }
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37
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38 /// The width of a Unicode character.
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39 #[derive(Copy, Clone, Debug)]
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40 pub enum Width {
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41 /// Narrow, taking up 1 terminal column.
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42 Narrow,
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43 /// Wide, taking up 2 terminal columns.
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44 Wide,
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45 }
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46
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47 impl Default for Encoder {
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48 fn default() -> Self {
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49 Self {
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50 local_encoding: Encoding::Utf8,
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51 decoding_mode: Mode::Strict,
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52 ambiguous_width: Width::Narrow,
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53 }
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54 }
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55 }
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56
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57 impl Encoder {
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58 /// Creates an encoder from environment variables.
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59 pub fn from_env() -> Result<Self, HgError> {
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60 let default = Encoder::default();
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61 let local_encoding = match std::env::var_os("HGENCODING") {
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62 None => default.local_encoding,
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63 Some(s)
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64 if s.eq_ignore_ascii_case("utf-8")
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65 || s.eq_ignore_ascii_case("utf8") =>
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66 {
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67 Encoding::Utf8
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68 }
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69 Some(s) if s.eq_ignore_ascii_case("ascii") => Encoding::Ascii,
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70 Some(s) => {
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71 return Err(HgError::unsupported(format!(
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72 "HGENCODING value '{}' is not supported",
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73 s.to_string_lossy()
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74 )))
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75 }
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76 };
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77 let decoding_mode = match std::env::var_os("HGENCODINGMODE") {
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78 None => default.decoding_mode,
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79 Some(s) if s == "strict" => Mode::Strict,
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80 Some(s) if s == "replace" => Mode::Replace,
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81 Some(s) => {
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82 return Err(HgError::abort_simple(format!(
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83 "HGENCODINGMODE value '{}' is not supported",
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84 s.to_string_lossy()
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85 )))
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86 }
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87 };
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88 let ambiguous_width = match std::env::var_os("HGENCODINGAMBIGUOUS") {
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89 None => default.ambiguous_width,
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90 Some(s) if s == "narrow" => Width::Narrow,
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91 Some(s) if s == "wide" => Width::Wide,
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92 Some(s) => {
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93 return Err(HgError::abort_simple(format!(
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94 "HGENCODINGAMBIGUOUS value '{}' is not supported",
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95 s.to_string_lossy()
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96 )))
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97 }
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98 };
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99 Ok(Self {
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100 local_encoding,
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101 decoding_mode,
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102 ambiguous_width,
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103 })
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104 }
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105
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106 /// Decodes an internal UTF-8 string from bytes.
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107 pub fn decode_internal<'a>(
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108 &self,
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109 bytes: &'a [u8],
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110 ) -> Result<&'a str, HgError> {
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111 decode_utf8(bytes).map_err(HgError::corrupted)
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112 }
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113
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114 /// Converts a string from internal UTF-8 to the local character encoding.
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115 pub fn to_local<'a>(&self, str: &'a str) -> Cow<'a, [u8]> {
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116 match self.local_encoding {
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117 Encoding::Utf8 => Cow::Borrowed(str.as_bytes()),
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118 Encoding::Ascii => {
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119 if str.is_ascii() {
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120 Cow::Borrowed(str.as_bytes())
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121 } else {
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122 Cow::Owned(codepoints_to_ascii_lossy(str).into_bytes())
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123 }
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124 }
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125 }
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126 }
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127
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128 /// Converts a string from the local character encoding to UTF-8.
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129 pub fn from_local<'a>(
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130 &self,
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131 bytes: &'a [u8],
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132 ) -> Result<Cow<'a, str>, HgError> {
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133 match (self.local_encoding, self.decoding_mode) {
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134 (Encoding::Utf8, Mode::Strict) => Ok(Cow::Borrowed(
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135 decode_utf8(bytes).map_err(HgError::abort_simple)?,
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136 )),
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137 (Encoding::Utf8, Mode::Replace) => {
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138 Ok(String::from_utf8_lossy(bytes))
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139 }
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140 (Encoding::Ascii, Mode::Strict) => Ok(Cow::Borrowed(
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141 decode_ascii(bytes).map_err(HgError::abort_simple)?,
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142 )),
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143 (Encoding::Ascii, Mode::Replace) => {
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144 Ok(Cow::Owned(bytes_to_ascii_lossy(bytes)))
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145 }
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146 }
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147 }
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148
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149 /// Returns the column width of a string for display.
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150 pub fn column_width(&self, str: &str) -> usize {
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151 match self.ambiguous_width {
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152 Width::Narrow => str.width(),
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153 Width::Wide => str.width_cjk(),
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154 }
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155 }
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156
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157 /// Returns the column width if `bytes` can be decoded as UTF-8, otherwise
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158 /// just returns the length in bytes.
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159 pub fn column_width_bytes(&self, bytes: &[u8]) -> usize {
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160 match str::from_utf8(bytes) {
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161 Ok(str) => self.column_width(str),
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162 Err(_) => bytes.len(),
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163 }
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164 }
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165 }
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166
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167 /// Decodes bytes as UTF-8 or returns a detailed error message.
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168 fn decode_utf8(bytes: &[u8]) -> Result<&str, String> {
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169 str::from_utf8(bytes).map_err(|err| {
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170 format!(
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171 "invalid UTF-8 at offset {}: \"{}\"",
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172 err.valid_up_to(),
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173 str::from_utf8(&bytes.escaped_bytes()).unwrap()
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174 )
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175 })
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176 }
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177
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178 /// Decodes bytes as ASCII or returns a detailed error message.
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179 fn decode_ascii(bytes: &[u8]) -> Result<&str, String> {
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180 // TODO: Use `as_ascii` https://github.com/rust-lang/rust/issues/110998
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181 if bytes.is_ascii() {
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182 // Safety: Just checked that it's ASCII.
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183 let str = unsafe { str::from_utf8_unchecked(bytes) };
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184 Ok(str)
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185 } else {
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186 Err(format!(
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187 "invalid ASCII: \"{}\"",
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188 str::from_utf8(&bytes.escaped_bytes()).unwrap()
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189 ))
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190 }
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191 }
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192
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193 /// Replaces all non-ASCII codepoints with '?'.
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194 fn codepoints_to_ascii_lossy(str: &str) -> String {
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195 let mut ascii = String::new();
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196 for char in str.chars() {
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197 ascii.push(if char.is_ascii() { char } else { '?' });
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198 }
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199 ascii
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200 }
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201
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202 /// Replaces all non-ASCII bytes with '?'.
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203 fn bytes_to_ascii_lossy(bytes: &[u8]) -> String {
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204 let mut ascii = String::new();
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205 for &b in bytes {
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206 ascii.push(if b.is_ascii() { b as char } else { '?' });
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207 }
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208 ascii
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209 }
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210
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211 #[cfg(test)]
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212 mod tests {
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213 use super::*;
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214
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215 #[test]
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216 fn test_decode_internal() {
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217 let encoder = Encoder::default();
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218 assert_eq!(encoder.decode_internal(b"").unwrap(), "");
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219 assert_eq!(encoder.decode_internal(b"\xc3\xa9").unwrap(), "é");
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220 match encoder.decode_internal(b"A\xc3") {
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221 Ok(_) => panic!("expected an error"),
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222 Err(HgError::CorruptedRepository(message)) => {
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223 assert_eq!(message, "invalid UTF-8 at offset 1: \"A\\xc3\"")
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224 }
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225 Err(_) => panic!("expected a CorruptedRepository error"),
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226 }
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227 }
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228
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229 #[test]
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230 fn test_to_local() {
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231 let encoder = Encoder::default();
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232 assert_eq!(encoder.to_local("").as_ref(), b"");
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233 assert_eq!(encoder.to_local("é").as_ref(), b"\xc3\xa9");
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234 }
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235
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236 #[test]
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237 fn test_from_local() {
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238 let encoder = Encoder::default();
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239 assert_eq!(encoder.from_local(b"").unwrap(), "");
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240 assert_eq!(encoder.from_local(b"\xc3\xa9").unwrap(), "é");
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241 match encoder.from_local(b"A\xc3") {
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242 Ok(_) => panic!("expected an error"),
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243 Err(HgError::Abort { message, .. }) => {
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244 assert_eq!(message, "invalid UTF-8 at offset 1: \"A\\xc3\"")
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245 }
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246 Err(_) => panic!("expected a CorruptedRepository error"),
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247 }
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248 }
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249
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250 #[test]
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251 fn test_from_local_replace() {
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252 let encoder = Encoder {
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253 decoding_mode: Mode::Replace,
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254 ..Default::default()
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255 };
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256 assert_eq!(encoder.from_local(b"A\xc3").unwrap(), "A\u{fffd}");
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257 }
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258
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259 #[test]
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260 fn test_column_width() {
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261 let encoder = Encoder::default();
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262 assert_eq!(encoder.column_width(""), 0);
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263 assert_eq!(encoder.column_width("a"), 1);
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264 assert_eq!(encoder.column_width("ab"), 2);
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265 assert_eq!(encoder.column_width("été"), 3);
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266 assert_eq!(encoder.column_width("\u{1f496}"), 2);
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267 }
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268
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269 #[test]
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270 fn test_column_width_ambiguous() {
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271 let narrow_encoder = Encoder {
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272 ambiguous_width: Width::Narrow,
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273 ..Default::default()
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274 };
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275 assert_eq!(narrow_encoder.column_width("\u{2606}"), 1);
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276
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277 let wide_encoder = Encoder {
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278 ambiguous_width: Width::Wide,
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279 ..Default::default()
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280 };
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281 assert_eq!(wide_encoder.column_width("\u{2606}"), 2);
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282 }
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283
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284 #[test]
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285 fn test_column_width_bytes() {
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286 let encoder = Encoder::default();
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287 assert_eq!(encoder.column_width_bytes(b""), 0);
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288 assert_eq!(encoder.column_width_bytes("été".as_bytes()), 3);
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289 assert_eq!(encoder.column_width_bytes(b"A\xc3"), 2);
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290 }
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291 }
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