1 function trim1(s)
2 return (s:gsub("^%s*(.-)%s*$", "%1"))
3 end
4 -- from PiL2 20.4
5
6 function trim2(s)
7 return s:match "^%s*(.-)%s*$"
8 end
9 -- variant of trim1 (match)
10
11 function trim3(s)
12 return s:gsub("^%s+", ""):gsub("%s+$", "")
13 end
14 -- two gsub's
15
16 function trim4(s)
17 return s:match"^%s*(.*)":match"(.-)%s*$"
18 end
19 -- variant of trim3 (match)
20
21 function trim5(s)
22 return s:match'^%s*(.*%S)' or ''
23 end
24 -- warning: has bad performance when s:match'^%s*$' and #s is large
25
26 function trim6(s)
27 return s:match'^()%s*$' and '' or s:match'^%s*(.*%S)'
28 end
29 -- fixes performance problem in trim5.
30 -- note: the '()' avoids the overhead of default string capture.
31 -- This overhead is small, ~ 10% for successful whitespace match call
32 -- alone, and may not be noticeable in the overall benchmarks here,
33 -- but there's little harm either. Instead replacing the first `match`
34 -- with a `find` has a similar effect, but that requires localizing
35 -- two functions in the trim7 variant below.
36
37 local match = string.match
38 function trim7(s)
39 return match(s,'^()%s*$') and '' or match(s,'^%s*(.*%S)')
40 end
41 -- variant of trim6 (localize functions)
42
43 local find = string.find
44 local sub = string.sub
45 function trim8(s)
46 local i1,i2 = find(s,'^%s*')
47 if i2 >= i1 then s = sub(s,i2+1) end
48 local i1,i2 = find(s,'%s*$')
49 if i2 >= i1 then s = sub(s,1,i1-1) end
50 return s
51 end
52 -- based on penlight 0.7.2
53
54 function trim9(s)
55 local _,i1 = find(s,'^%s*')
56 local i2 = find(s,'%s*$')
57 return sub(s,i1+1,i2-1)
58 end
59 -- simplification of trim8
60
61 function trim10(s)
62 local a = s:match('^%s*()')
63 local b = s:match('()%s*$', a)
64 return s:sub(a,b-1)
65 end
66 -- variant of trim9 (match)
67
68 function trim11(s)
69 local n = s:find"%S"
70 return n and s:match(".*%S", n) or ""
71 end
72 -- variant of trim6 (use n position)
73 -- http://lua-users.org/lists/lua-l/2009-12/msg00904.html
74
75 function trim12(s)
76 local from = s:match"^%s*()"
77 return from > #s and "" or s:match(".*%S", from)
78 end
79 -- variant of trim11 (performs better for all
80 -- whitespace string). See Roberto's comments
81 -- on ^%s*$" v.s. "%S" performance:
82 -- http://lua-users.org/lists/lua-l/2009-12/msg00921.html
83
84 do
85 require 'lpeg'
86 local space = lpeg.S' \t\n\v\f\r'
87 local nospace = 1 - space
88 local ptrim = space^0 * lpeg.C((space^0 * nospace^1)^0)
89 local match = lpeg.match
90 function trim13(s)
91 return match(ptrim, s)
92 end
93 end
94 -- lpeg. based on http://lua-users.org/lists/lua-l/2009-12/msg00921.html
95
96 do
97 require 'lpeg'
98 require 're'
99 local ptrim = re.compile"%s* {(%s* %S+)*}"
100 local match = lpeg.match
101 function trim14(s)
102 return match(ptrim, s)
103 end
104 end
105 -- variant with re module.
106
107 require 'trim'
108 local trim15 = trim
109 -- C implementation (see separate trim.c file)
110
111
112 -- test utilities
113
114 local function trimtest(trim)
115 assert(trim'' == '')
116 assert(trim' ' == '')
117 assert(trim' ' == '')
118 assert(trim'a' == 'a')
119 assert(trim' a' == 'a')
120 assert(trim'a ' == 'a')
121 assert(trim' a ' == 'a')
122 assert(trim' a ' == 'a')
123 assert(trim' ab cd ' == 'ab cd')
124 assert(trim' \t\r\n\f\va\000b \r\t\n\f\v' == 'a\000b')
125 end
126
127 local function perftest(f, s)
128 local time = os.clock -- os.time or os.clock
129 local t1 = time()
130 for i=1,100000 do
131 f(s)f(s)f(s)f(s)f(s)f(s)f(s)f(s)f(s)f(s)
132 end
133 local dt = time() - t1
134 io.stdout:write(string.format("%4.1f",dt) .. ' ')
135 end
136
137 local trims = {trim1, trim2, trim3, trim4, trim5, trim6, trim7,
138 trim8, trim9, trim10, trim11, trim12, trim13, trim14, trim15}
139
140 -- correctness tests
141 for _,trim in ipairs(trims) do
142 trimtest(trim)
143 end
144
145 -- performance tests
146 for j=1,3 do
147 for i,trim in ipairs(trims) do
148 io.stdout:write(string.format("%2d",i) .. ": ")
149 perftest(trim, "")
150 perftest(trim, "abcdef")
151 perftest(trim, " abcdef ")
152 perftest(trim, "abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef")
153 perftest(trim, " a b c d e f g h i j k l m n o p q r s t u v w x y z A B C ")
154 perftest(trim, " a ")
155 perftest(trim, " ")
156 print()
157 end
158 end
