mirror of https://github.com/aya-rs/aya
lib: Add display hints
This change adds optional display hints:
* `{:x}`, `{:X}` - for hex representation of numbers
* `{:ipv4}`, `{:IPv4}` - for IPv4 addresses
* `{:ipv6}`, `{:IPv6}` - for IPv6 addresses
It also gets rid of dyn-fmt and instead comes with our own parser
implementation.
Tested on: https://github.com/vadorovsky/aya-examples/tree/main/tc
Signed-off-by: Michal Rostecki <vadorovsky@gmail.com>
pull/372/head
Michal Rostecki
3 years ago
committed by
Alessandro Decina
parent
944d6b8a16
commit
83ec27f06b
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[package]
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name = "aya-log-parser"
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version = "0.1.11-dev.0"
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edition = "2018"
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[dependencies]
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aya-log-common = { path = "../aya-log-common" }
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[lib]
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path = "src/lib.rs"
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use std::str;
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use aya_log_common::DisplayHint;
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/// A parsed formatting parameter (contents of `{` `}` block).
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct Parameter {
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/// The display hint, e.g. ':ipv4', ':x'.
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pub hint: DisplayHint,
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}
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub enum Fragment {
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/// A literal string (eg. `"literal "` in `"literal {}"`).
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Literal(String),
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/// A format parameter.
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Parameter(Parameter),
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}
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fn push_literal(frag: &mut Vec<Fragment>, unescaped_literal: &str) -> Result<(), String> {
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// Replace `{{` with `{` and `}}` with `}`. Single braces are errors.
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// Scan for single braces first. The rest is trivial.
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let mut last_open = false;
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let mut last_close = false;
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for c in unescaped_literal.chars() {
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match c {
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'{' => last_open = !last_open,
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'}' => last_close = !last_close,
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_ => {
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if last_open {
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return Err("unmatched `{` in format string".into());
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}
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if last_close {
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return Err("unmatched `}` in format string".into());
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}
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}
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}
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}
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// Handle trailing unescaped `{` or `}`.
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if last_open {
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return Err("unmatched `{` in format string".into());
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}
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if last_close {
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return Err("unmatched `}` in format string".into());
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}
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let literal = unescaped_literal.replace("{{", "{").replace("}}", "}");
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frag.push(Fragment::Literal(literal));
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Ok(())
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}
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/// Parses the display hint (e.g. the `ipv4` in `{:ipv4}`).
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fn parse_display_hint(s: &str) -> Result<DisplayHint, String> {
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Ok(match s {
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"x" => DisplayHint::LowerHex,
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"X" => DisplayHint::UpperHex,
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"ipv4" => DisplayHint::Ipv4,
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"ipv6" => DisplayHint::Ipv6,
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_ => return Err(format!("unknown display hint: {:?}", s)),
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})
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}
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/// Parse `Param` from the given `&str` which can specify an optional format
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/// like `:x` or `:ipv4` (without curly braces, which are parsed by the `parse`
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/// function).
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fn parse_param(mut input: &str) -> Result<Parameter, String> {
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const HINT_PREFIX: &str = ":";
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// Then, optional hint
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let mut hint = DisplayHint::Default;
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if input.starts_with(HINT_PREFIX) {
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// skip the prefix
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input = &input[HINT_PREFIX.len()..];
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if input.is_empty() {
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return Err("malformed format string (missing display hint after ':')".into());
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}
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hint = parse_display_hint(input)?;
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} else if !input.is_empty() {
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return Err(format!("unexpected content {:?} in format string", input));
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}
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Ok(Parameter { hint })
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}
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/// Parses the given format string into string literals and parameters specified
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/// by curly braces (with optional format hints like `:x` or `:ipv4`).
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pub fn parse(format_string: &str) -> Result<Vec<Fragment>, String> {
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let mut fragments = Vec::new();
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// Index after the `}` of the last format specifier.
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let mut end_pos = 0;
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let mut chars = format_string.char_indices();
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while let Some((brace_pos, ch)) = chars.next() {
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if ch != '{' {
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// Part of a literal fragment.
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continue;
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}
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// Peek at the next char.
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if chars.as_str().starts_with('{') {
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// Escaped `{{`, also part of a literal fragment.
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chars.next();
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continue;
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}
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if brace_pos > end_pos {
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// There's a literal fragment with at least 1 character before this
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// parameter fragment.
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let unescaped_literal = &format_string[end_pos..brace_pos];
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push_literal(&mut fragments, unescaped_literal)?;
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}
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// Else, this is a format specifier. It ends at the next `}`.
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let len = chars
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.as_str()
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.find('}')
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.ok_or("missing `}` in format string")?;
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end_pos = brace_pos + 1 + len + 1;
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// Parse the contents inside the braces.
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let param_str = &format_string[brace_pos + 1..][..len];
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let param = parse_param(param_str)?;
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fragments.push(Fragment::Parameter(param));
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}
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// Trailing literal.
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if end_pos != format_string.len() {
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push_literal(&mut fragments, &format_string[end_pos..])?;
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}
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Ok(fragments)
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_parse() {
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assert_eq!(
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parse("foo {} bar {:x} test {:X} ayy {:ipv4} lmao {:ipv6} {{}} {{something}}"),
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Ok(vec![
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Fragment::Literal("foo ".into()),
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Fragment::Parameter(Parameter {
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hint: DisplayHint::Default
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}),
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Fragment::Literal(" bar ".into()),
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Fragment::Parameter(Parameter {
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hint: DisplayHint::LowerHex
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}),
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Fragment::Literal(" test ".into()),
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Fragment::Parameter(Parameter {
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hint: DisplayHint::UpperHex
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}),
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Fragment::Literal(" ayy ".into()),
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Fragment::Parameter(Parameter {
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hint: DisplayHint::Ipv4
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}),
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Fragment::Literal(" lmao ".into()),
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Fragment::Parameter(Parameter {
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hint: DisplayHint::Ipv6
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}),
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Fragment::Literal(" {{}} {{something}}".into()),
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])
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);
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assert!(parse("foo {:}").is_err());
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assert!(parse("foo { bar").is_err());
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assert!(parse("foo } bar").is_err());
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assert!(parse("foo { bar }").is_err());
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}
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}
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