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std.json: expose encodeJsonString and encodeJsonStringChars

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Expose 2 functions from std.json.  These functions take a slice of bytes
and forward them to a given writer as a JSON encoded string.

The use case I have for this is in a custom JsonStringWriter.  This writer
takes data and automatically encodes it as JSON string characters and
forwards it to an underlying writer.  I use this JsonStringWriter in
combination with std.fmt.format to go directly from a format string/arg
pair to JSON.  This way I don't have to format my string into a separate
buffer first and encode it afterwards, which avoids the need to create
a temporary buffer to hold the unencoded but formatted string.
This commit is contained in:
Jonathan Marler 2022-06-30 15:02:09 -06:00 committed by Veikka Tuominen
parent a2ab9e36fa
commit f598234ee8
1 changed files with 27 additions and 21 deletions
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48
lib/std/json.zig
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@ -2163,45 +2163,51 @@ fn outputUnicodeEscape(
}
}
fn outputJsonString(value: []const u8, options: StringifyOptions, out_stream: anytype) !void {
try out_stream.writeByte('\"');
/// Write `string` to `writer` as a JSON encoded string.
pub fn encodeJsonString(string: []const u8, options: StringifyOptions, writer: anytype) !void {
try writer.writeByte('\"');
try encodeJsonStringChars(string, options, writer);
try writer.writeByte('\"');
}
/// Write `chars` to `writer` as JSON encoded string characters.
pub fn encodeJsonStringChars(chars: []const u8, options: StringifyOptions, writer: anytype) !void {
var i: usize = 0;
while (i < value.len) : (i += 1) {
switch (value[i]) {
while (i < chars.len) : (i += 1) {
switch (chars[i]) {
// normal ascii character
0x20...0x21, 0x23...0x2E, 0x30...0x5B, 0x5D...0x7F => |c| try out_stream.writeByte(c),
0x20...0x21, 0x23...0x2E, 0x30...0x5B, 0x5D...0x7F => |c| try writer.writeByte(c),
// only 2 characters that *must* be escaped
'\\' => try out_stream.writeAll("\\\\"),
'\"' => try out_stream.writeAll("\\\""),
'\\' => try writer.writeAll("\\\\"),
'\"' => try writer.writeAll("\\\""),
// solidus is optional to escape
'/' => {
if (options.string.String.escape_solidus) {
try out_stream.writeAll("\\/");
try writer.writeAll("\\/");
} else {
try out_stream.writeByte('/');
try writer.writeByte('/');
}
},
// control characters with short escapes
// TODO: option to switch between unicode and 'short' forms?
0x8 => try out_stream.writeAll("\\b"),
0xC => try out_stream.writeAll("\\f"),
'\n' => try out_stream.writeAll("\\n"),
'\r' => try out_stream.writeAll("\\r"),
'\t' => try out_stream.writeAll("\\t"),
0x8 => try writer.writeAll("\\b"),
0xC => try writer.writeAll("\\f"),
'\n' => try writer.writeAll("\\n"),
'\r' => try writer.writeAll("\\r"),
'\t' => try writer.writeAll("\\t"),
else => {
const ulen = std.unicode.utf8ByteSequenceLength(value[i]) catch unreachable;
const ulen = std.unicode.utf8ByteSequenceLength(chars[i]) catch unreachable;
// control characters (only things left with 1 byte length) should always be printed as unicode escapes
if (ulen == 1 or options.string.String.escape_unicode) {
const codepoint = std.unicode.utf8Decode(value[i .. i + ulen]) catch unreachable;
try outputUnicodeEscape(codepoint, out_stream);
const codepoint = std.unicode.utf8Decode(chars[i .. i + ulen]) catch unreachable;
try outputUnicodeEscape(codepoint, writer);
} else {
try out_stream.writeAll(value[i .. i + ulen]);
try writer.writeAll(chars[i .. i + ulen]);
}
i += ulen - 1;
},
}
}
try out_stream.writeByte('\"');
}
pub fn stringify(
@ -2288,7 +2294,7 @@ pub fn stringify(
if (child_options.whitespace) |child_whitespace| {
try child_whitespace.outputIndent(out_stream);
}
try outputJsonString(Field.name, options, out_stream);
try encodeJsonString(Field.name, options, out_stream);
try out_stream.writeByte(':');
if (child_options.whitespace) |child_whitespace| {
if (child_whitespace.separator) {
@ -2321,7 +2327,7 @@ pub fn stringify(
// TODO: .Many when there is a sentinel (waiting for https://github.com/ziglang/zig/pull/3972)
.Slice => {
if (ptr_info.child == u8 and options.string == .String and std.unicode.utf8ValidateSlice(value)) {
try outputJsonString(value, options, out_stream);
try encodeJsonString(value, options, out_stream);
return;
}