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September 25, 2012 01:01
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An attempt at faster Julia IO
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# Chris DuBois | |
# September 2012 | |
# Inspired by: http://vijayinterviewquestions.blogspot.com/2007/07/write-your-own-c-program-to-implement.html | |
function atoi(s) | |
i = 0 | |
L = strlen(s) | |
# skip preceding whitespaece | |
a = 1 | |
while s[a] == ' ' | |
a+=1 | |
end | |
j = a | |
while j <= L | |
# skip trailing non digits | |
if s[j] < '0' || s[j] > '9' | |
j = L + 1 | |
else | |
i = (i << 3) + (i << 1) + s[j] - '0' | |
j += 1 | |
end | |
end | |
return i | |
end | |
@assert atoi("390709") == 390709 | |
@assert atoi(" 390709") == 390709 | |
@assert atoi(" 390709 ") == 390709 | |
@assert atoi(" 390709 lxkjd") == 390709 | |
function atof(s) | |
out = Array(Float64,1) | |
ccall(:jl_strtod, Int32, (Ptr{Uint8},Ptr{Float64}), s, out) | |
out[1] | |
end | |
@assert atof("1.234") == 1.234 | |
@assert atof(" 1.234") == 1.234 | |
@assert atof(" 1.234 ") == 1.234 | |
@assert atof(" 1 ") == 1.0 | |
# Read a delimited file with known types in each column. | |
# Return a Dict with an element for every column. | |
# TODO: how to handle empty final lines | |
function dlm2dict(filename, types, dlm::Char, header) | |
d = Dict() | |
io = open(filename) | |
if header | |
cn = split(readline(io),dlm) | |
else | |
cn = [strcat("column_",x) for x in 1:length(types)] | |
end | |
for i in 1:length(cn) | |
d[cn[i]] = Array(types[i], 0) | |
end | |
for line in each_line(io) | |
pos = 1 | |
for i in 1:length(cn) | |
if types[i] == Int64 | |
push(d[cn[i]], atoi(line[pos:end])) | |
pos = strchr(line, dlm, pos) + 1 | |
elseif types[i] == Float64 | |
push(d[cn[i]], atof(line[pos:end])) | |
pos = strchr(line, dlm, pos) + 1 | |
else | |
e = strchr(line, dlm, pos) | |
push(d[cn[i]], line[pos:e]) | |
pos = e + 1 | |
end | |
end | |
end | |
return d | |
end |
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