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feat: make signs significant for byte offsets
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@ErichDonGubler @sharkdp
ErichDonGubler authored and sharkdp committed Aug 15, 2020
1 parent 7217a60 commit 153b1cc
Showing 1 changed file with 122 additions and 66 deletions.
188 changes: 122 additions & 66 deletions src/bin/hexyl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,8 @@ fn run() -> Result<(), AnyhowError> {
.value_name("N")
.help(
"Skip the first N bytes of the input. The N argument can also include \
a unit (see `--length` for details)",
a unit (see `--length` for details)\n\
A negative value is valid and will seek from the end of the file.",
),
)
.arg(
Expand Down Expand Up @@ -111,7 +112,9 @@ fn run() -> Result<(), AnyhowError> {
.value_name("N")
.help(
"Add N bytes to the displayed file position. The N argument can also \
include a unit (see `--length` for details)",
include a unit (see `--length` for details)\n\
A negative value is valid and calculates an offset relative to the \
end of the file.",
),
);

Expand Down Expand Up @@ -144,29 +147,43 @@ fn run() -> Result<(), AnyhowError> {
let skip_arg = matches
.value_of("skip")
.map(|s| {
parse_byte_count(s, block_size).context(anyhow!(
parse_byte_offset(s, block_size).context(anyhow!(
"failed to parse `--skip` arg {:?} as byte count",
s
))
})
.transpose()?;

if let Some(skip) = skip_arg {
reader.seek(SeekFrom::Current(skip.into_inner()))?;
}
let default_display_offset = if let Some(ByteOffset { kind, value }) = skip_arg {
let value = value.into_inner();
reader.seek(match kind {
ByteOffsetKind::ForwardFromBeginning | ByteOffsetKind::ForwardFromLastOffset => {
SeekFrom::Current(value)
}
ByteOffsetKind::BackwardFromEnd => SeekFrom::End(value.checked_neg().unwrap()),
})?
} else {
0
};

let parse_byte_count = |s| -> Result<u64, AnyhowError> {
Ok(parse_byte_offset(s, block_size)?
.assume_forward_offset_from_start()?.into())
};

let mut reader = if let Some(length) = matches
.value_of("length")
.or_else(|| matches.value_of("bytes"))
.map(|s| {
parse_byte_count(s, block_size).context(anyhow!(
"failed to parse `--length` arg {:?} as byte count",
s
))
parse_byte_count(s)
.context(anyhow!(
"failed to parse `--length` arg {:?} as byte count",
s
))
})
.transpose()?
{
Box::new(reader.take(length.into()))
Box::new(reader.take(length))
} else {
reader.into_inner()
};
Expand All @@ -188,14 +205,13 @@ fn run() -> Result<(), AnyhowError> {
let display_offset = matches
.value_of("display_offset")
.map(|s| {
parse_byte_count(s, block_size).context(anyhow!(
parse_byte_count(s).context(anyhow!(
"failed to parse `--display-offset` arg {:?} as byte count",
s
))
})
.transpose()?
.or(skip_arg)
.unwrap_or_default()
.unwrap_or(default_display_offset)
.into();

let stdout = io::stdout();
Expand Down Expand Up @@ -259,14 +275,41 @@ impl Into<u64> for PositiveI64 {

const HEX_PREFIX: &str = "0x";

#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
enum ByteOffsetKind {
ForwardFromBeginning,
ForwardFromLastOffset,
BackwardFromEnd,
}

#[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
struct ByteOffset {
value: PositiveI64,
kind: ByteOffsetKind,
}

#[derive(Clone, Debug, ThisError)]
#[error("negative offset specified, but only positive offsets (counts) are accepted in this context")]
struct NegativeOffsetSpecifiedError;

impl ByteOffset {
fn assume_forward_offset_from_start(&self) -> Result<PositiveI64, NegativeOffsetSpecifiedError> {
let &Self { value, kind } = self;
match kind {
ByteOffsetKind::ForwardFromBeginning | ByteOffsetKind::ForwardFromLastOffset => {
Ok(value)
}
ByteOffsetKind::BackwardFromEnd => Err(NegativeOffsetSpecifiedError),
}
}
}

#[derive(Clone, Debug, Eq, PartialEq, ThisError)]
enum ByteCountParseError {
enum ByteOffsetParseError {
#[error("no character data found, did you forget to write it?")]
Empty,
#[error("no digits found after sign, did you forget to write them?")]
EmptyAfterSign,
#[error("negative byte offsets are not accepted (yet)")]
Negative,
#[error(
"found {0:?} sign after hex prefix ({:?}); signs should go before it",
HEX_PREFIX
Expand All @@ -284,24 +327,34 @@ enum ByteCountParseError {
UnitMultiplicationOverflow,
}

fn parse_byte_count(n: &str, block_size: PositiveI64) -> Result<PositiveI64, ByteCountParseError> {
use ByteCountParseError::*;
fn parse_byte_offset(n: &str, block_size: PositiveI64) -> Result<ByteOffset, ByteOffsetParseError> {
use ByteOffsetParseError::*;

let n = {
let (n, kind) = {
let mut chars = n.chars();
match chars.next() {
Some('+') => {
if chars.clone().next().is_none() {
return Err(EmptyAfterSign);
}
chars.as_str()
let next_char = chars.next();
let check_empty_after_sign = || {
if chars.clone().next().is_none() {
Err(EmptyAfterSign)
} else {
Ok(chars.as_str())
}
Some('-') => return Err(Negative),
};
match next_char {
Some('+') => (check_empty_after_sign()?, ByteOffsetKind::ForwardFromLastOffset),
Some('-') => (check_empty_after_sign()?, ByteOffsetKind::BackwardFromEnd),
None => return Err(Empty),
_ => n,
_ => (n, ByteOffsetKind::ForwardFromBeginning),
}
};

let into_byte_offset = |value| {
Ok(ByteOffset {
value: PositiveI64::new(value).unwrap(),
kind,
})
};

if n.starts_with(HEX_PREFIX) {
let n = &n[HEX_PREFIX.len()..];
let mut chars = n.chars();
Expand All @@ -316,7 +369,7 @@ fn parse_byte_count(n: &str, block_size: PositiveI64) -> Result<PositiveI64, Byt
_ => (),
}
return i64::from_str_radix(n, 16)
.map(|x| Ok(PositiveI64::new(x).unwrap()))
.map(into_byte_offset)
.map_err(ParseNum)?;
}

Expand Down Expand Up @@ -355,7 +408,7 @@ fn parse_byte_count(n: &str, block_size: PositiveI64) -> Result<PositiveI64, Byt
(Ok(num), Ok((_raw_unit, unit_multiplier))) => num
.checked_mul(unit_multiplier)
.ok_or_else(|| UnitMultiplicationOverflow)
.and_then(|x| PositiveI64::new(x).ok_or(Negative)),
.and_then(into_byte_offset),
(Ok(_), Err(e)) => Err(e),
(Err(e), Ok((raw_unit, _unit_multiplier))) => match raw_unit {
Some(raw_unit) if num.is_empty() => Err(EmptyWithUnit(raw_unit.to_owned())),
Expand All @@ -366,74 +419,77 @@ fn parse_byte_count(n: &str, block_size: PositiveI64) -> Result<PositiveI64, Byt
}

#[test]
fn test_parse_byte_count() {
use ByteCountParseError::*;
fn test_parse_byte_offset() {
use ByteOffsetParseError::*;

macro_rules! success {
($input: expr, $expected: expr) => {
success!($input, 512, $expected)
($input: expr, $expected_kind: ident $expected_value: expr) => {
success!($input, $expected_kind $expected_value; block_size: 512)
};
($input: expr, $block_size: expr, $expected: expr) => {
($input: expr, $expected_kind: ident $expected_value: expr; block_size: $block_size: expr) => {
assert_eq!(
parse_byte_count($input, PositiveI64::new($block_size).unwrap()),
Ok(PositiveI64::new($expected).unwrap()),
parse_byte_offset($input, PositiveI64::new($block_size).unwrap()),
Ok(
ByteOffset {
value: PositiveI64::new($expected_value).unwrap(),
kind: ByteOffsetKind::$expected_kind,
}
),
);
};
}

macro_rules! error {
($input: expr, $expected_err: expr) => {
assert_eq!(
parse_byte_count($input, PositiveI64::new(512).unwrap()),
parse_byte_offset($input, PositiveI64::new(512).unwrap()),
Err($expected_err),
);
};
}

success!("0", 0);
success!("1", 1);
success!("1", 1);
success!("100", 100);
success!("+100", 100);
success!("0", ForwardFromBeginning 0);
success!("1", ForwardFromBeginning 1);
success!("1", ForwardFromBeginning 1);
success!("100", ForwardFromBeginning 100);
success!("+100", ForwardFromLastOffset 100);

success!("0x0", 0);
success!("0xf", 15);
success!("0xdeadbeef", 3_735_928_559);
success!("0x0", ForwardFromBeginning 0);
success!("0xf", ForwardFromBeginning 15);
success!("0xdeadbeef", ForwardFromBeginning 3_735_928_559);

success!("1KB", 1000);
success!("2MB", 2000000);
success!("3GB", 3000000000);
success!("4TB", 4000000000000);
success!("+4TB", 4000000000000);
success!("1KB", ForwardFromBeginning 1000);
success!("2MB", ForwardFromBeginning 2000000);
success!("3GB", ForwardFromBeginning 3000000000);
success!("4TB", ForwardFromBeginning 4000000000000);
success!("+4TB", ForwardFromLastOffset 4000000000000);

success!("1GiB", 1073741824);
success!("2TiB", 2199023255552);
success!("+2TiB", 2199023255552);
success!("1GiB", ForwardFromBeginning 1073741824);
success!("2TiB", ForwardFromBeginning 2199023255552);
success!("+2TiB", ForwardFromLastOffset 2199023255552);

success!("0xff", 255);
success!("0xEE", 238);
success!("+0xFF", 255);
success!("0xff", ForwardFromBeginning 255);
success!("0xEE", ForwardFromBeginning 238);
success!("+0xFF", ForwardFromLastOffset 255);

success!("1block", 512, 512);
success!("2block", 512, 1024);
success!("1block", 4, 4);
success!("2block", 4, 8);
success!("1block", ForwardFromBeginning 512; block_size: 512);
success!("2block", ForwardFromBeginning 1024; block_size: 512);
success!("1block", ForwardFromBeginning 4; block_size: 4);
success!("2block", ForwardFromBeginning 8; block_size: 4);

// empty string is invalid
error!("", Empty);
// These are also bad.
error!("+", EmptyAfterSign);
error!("-", Negative);
error!("-", EmptyAfterSign);
error!("K", InvalidNumAndUnit("K".to_owned()));
error!("k", InvalidNumAndUnit("k".to_owned()));
error!("m", InvalidNumAndUnit("m".to_owned()));
error!("block", EmptyWithUnit("block".to_owned()));
// leading/trailing space is invalid
error!(" 0", InvalidNumAndUnit(" 0".to_owned()));
error!("0 ", InvalidUnit(" ".to_owned()));
// Negatives make no sense for byte counts
error!("-1", Negative);
error!("-0x-12", Negative);
// Signs after the hex prefix make no sense
error!("0x-12", SignFoundAfterHexPrefix('-'));
// This was previously accepted but shouldn't be.
error!("0x+12", SignFoundAfterHexPrefix('+'));
Expand All @@ -445,7 +501,7 @@ fn test_parse_byte_count() {
// multiplication overflows u64
error!("20000000TiB", UnitMultiplicationOverflow);

assert!(match parse_byte_count("99999999999999999999", PositiveI64::new(512).unwrap()) {
assert!(match parse_byte_offset("99999999999999999999", PositiveI64::new(512).unwrap()) {
// We can't check against the kind of the `ParseIntError`, so we'll just make sure it's the
// same as trying to do the parse directly.
Err(ParseNum(e)) => e == "99999999999999999999".parse::<i64>().unwrap_err(),
Expand Down

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