diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/pure/parseutils.nim | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/lib/pure/parseutils.nim b/lib/pure/parseutils.nim index 2bb23c626..c4d59d892 100644 --- a/lib/pure/parseutils.nim +++ b/lib/pure/parseutils.nim @@ -592,6 +592,71 @@ proc parseFloat*(s: openArray[char], number: var float): int {. if result != 0: number = bf +func toLowerAscii(c: char): char = + if c in {'A'..'Z'}: char(uint8(c) xor 0b0010_0000'u8) else: c + +func parseSize*(s: openArray[char], size: var int64, alwaysBin=false): int = + ## Parse a size qualified by binary or metric units into `size`. This format + ## is often called "human readable". Result is the number of processed chars + ## or 0 on parse errors and size is rounded to the nearest integer. Trailing + ## garbage like "/s" in "1k/s" is allowed and detected by `result < s.len`. + ## + ## To simplify use, following non-rare wild conventions, and since fractional + ## data like milli-bytes is so rare, unit matching is case-insensitive but for + ## the 'i' distinguishing binary-metric from metric (which cannot be 'I'). + ## + ## An optional trailing 'B|b' is ignored but processed. I.e., you must still + ## know if units are bytes | bits or infer this fact via the case of s[^1] (if + ## users can even be relied upon to use 'B' for byte and 'b' for bit or have + ## that be s[^1]). + ## + ## If `alwaysBin==true` then scales are always binary-metric, but e.g. "KiB" + ## is still accepted for clarity. If the value would exceed the range of + ## `int64`, `size` saturates to `int64.high`. Supported metric prefix chars + ## include k, m, g, t, p, e, z, y (but z & y saturate unless the number is a + ## small fraction). + ## + ## **See also:** + ## * https://en.wikipedia.org/wiki/Binary_prefix + ## * `formatSize module<strutils.html>`_ for formatting + runnableExamples: + var res: int64 # caller must still know if 'b' refers to bytes|bits + doAssert parseSize("10.5 MB", res) == 7 + doAssert res == 10_500_000 # decimal metric Mega prefix + doAssert parseSize("64 mib", res) == 6 + doAssert res == 67108864 # 64 shl 20 + doAssert parseSize("1G/h", res, true) == 2 # '/' stops parse + doAssert res == 1073741824 # 1 shl 30, forced binary metric + const prefix = "b" & "kmgtpezy" # byte|bit & lowCase metric-ish prefixes + const scaleM = [1.0, 1e3, 1e6, 1e9, 1e12, 1e15, 1e18, 1e21, 1e24] # 10^(3*idx) + const scaleB = [1.0, 1024, 1048576, 1073741824, 1099511627776.0, # 2^(10*idx) + 1125899906842624.0, 1152921504606846976.0, # ldexp? + 1.180591620717411303424e21, 1.208925819614629174706176e24] + var number: float + var scale = 1.0 + result = parseFloat(s, number) + if number < 0: # While parseFloat accepts negatives .. + result = 0 #.. we do not since sizes cannot be < 0 + if result > 0: + let start = result # Save spot to maybe unwind white to EOS + while result < s.len and s[result] in Whitespace: + inc result + if result < s.len: # Illegal starting char => unity + if (let si = prefix.find(s[result].toLowerAscii); si >= 0): + inc result # Now parse the scale + scale = if alwaysBin: scaleB[si] else: scaleM[si] + if result < s.len and s[result] == 'i': + scale = scaleB[si] # Switch from default to binary-metric + inc result + if result < s.len and s[result].toLowerAscii == 'b': + inc result # Skip optional '[bB]' + else: # Unwind result advancement when there.. + result = start #..is no unit to the end of `s`. + var sizeF = number * scale + 0.5 # Saturate to int64.high when too big + size = if sizeF > 9223372036854774784.0: int64.high else: sizeF.int64 +# Above constant=2^63-1024 avoids C UB; github.com/nim-lang/Nim/issues/20102 or +# stackoverflow.com/questions/20923556/math-pow2-63-1-math-pow2-63-512-is-true + type InterpolatedKind* = enum ## Describes for `interpolatedFragments` ## which part of the interpolated string is |