506 lines
16 KiB
Markdown
506 lines
16 KiB
Markdown
# V RegEx (Regular expression) 0.9c
|
|
|
|
[TOC]
|
|
|
|
## introduction
|
|
|
|
Write here the introduction... not today!! -_-
|
|
|
|
## Basic assumption
|
|
|
|
In this release, during the writing of the code some assumptions are made and are valid for all the features.
|
|
|
|
1. The matching stops at the end of the string not at the newline chars.
|
|
2. The basic elements of this regex engine are the tokens, in a query string a simple char is a token. The token is the atomic unit of this regex engine.
|
|
|
|
## Match positional limiter
|
|
|
|
The module supports the following features:
|
|
|
|
- `$` `^` delimiter
|
|
|
|
`^` (Caret.) Matches at the start of the string
|
|
|
|
`$` Matches at the end of the string
|
|
|
|
## Tokens
|
|
|
|
The tokens are the atomic units used by this regex engine and can be ones of the following:
|
|
|
|
### Simple char
|
|
|
|
this token is a simple single character like `a`.
|
|
|
|
### Char class (cc)
|
|
|
|
The cc match all the chars specified inside, it is delimited by square brackets `[ ]`
|
|
|
|
the sequence of chars in the class is evaluated with an OR operation.
|
|
|
|
For example, the following cc `[abc]` match any char that is `a` or `b` or `c` but doesn't match `C` or `z`.
|
|
|
|
Inside a cc is possible to specify a "range" of chars, for example `[ad-f]` is equivalent to write `[adef]`.
|
|
|
|
A cc can have different ranges at the same time like `[a-zA-z0-9]` that match all the lowercase,uppercase and numeric chars.
|
|
|
|
It is possible negate the cc using the caret char at the start of the cc like: `[^abc]` that matches every char that is not `a` or `b` or `c`.
|
|
|
|
A cc can contain meta-chars like: `[a-z\d]` that matches all the lowercase latin chars `a-z` and all the digits `\d`.
|
|
|
|
It is possible to mix all the properties of the char class together.
|
|
|
|
### Meta-chars
|
|
|
|
A meta-char is specified by a backslash before a char like `\w` in this case the meta-char is `w`.
|
|
|
|
A meta-char can match different type of chars.
|
|
|
|
* `\w` match an alphanumeric char `[a-zA-Z0-9]`
|
|
* `\W` match a non alphanumeric char
|
|
* `\d` match a digit `[0-9]`
|
|
* `\D` match a non digit
|
|
* `\s`match a space char, one of `[' ','\t','\n','\r','\v','\f']`
|
|
* `\S` match a non space char
|
|
* `\a` match only a lowercase char `[a-z]`
|
|
* `\A` match only an uppercase char `[A-Z]`
|
|
|
|
### Quantifier
|
|
|
|
Each token can have a quantifier that specify how many times the char can or must be matched.
|
|
|
|
#### **Short quantifier**
|
|
|
|
- `?` match 0 or 1 time, `a?b` match both `ab` or `b`
|
|
- `+` match at minimum 1 time, `a+` match both `aaa` or `a`
|
|
- `*` match 0 or more time, `a*b` match both `aaab` or `ab` or `b`
|
|
|
|
#### **Long quantifier**
|
|
|
|
- `{x}` match exactly x time, `a{2}` match `aa` but doesn't match `aaa` or `a`
|
|
- `{min,}` match at minimum min time, `a{2,}` match `aaa` or `aa` but doesn't match `a`
|
|
- `{,max}` match at least 0 time and maximum max time, `a{,2}` match `a` and `aa` but doesn't match `aaa`
|
|
- `{min,max}` match from min times to max times, `a{2,3}` match `aa` and `aaa` but doesn't match `a` or `aaaa`
|
|
|
|
a long quantifier may have a `greedy off` flag that is the `?` char after the brackets, `{2,4}?` means to match the minimum number possible tokens in this case 2.
|
|
|
|
### dot char
|
|
|
|
the dot is a particular meta char that match "any char", is more simple explain it with an example:
|
|
|
|
suppose to have `abccc ddeef` as source string to parse with regex, the following table show the query strings and the result of parsing source string.
|
|
|
|
| query string | result |
|
|
| ------------ | ------ |
|
|
| `.*c` | `abc` |
|
|
| `.*dd` | `abcc dd` |
|
|
| `ab.*e` | `abccc dde` |
|
|
| `ab.{3} .*e` | `abccc dde` |
|
|
|
|
the dot char match any char until the next token match is satisfied.
|
|
|
|
### OR token
|
|
|
|
the token `|` is a logic OR operation between two consecutive tokens, `a|b` match a char that is `a` or `b`.
|
|
|
|
The OR token can work in a "chained way": `a|(b)|cd ` test first `a` if the char is not `a` then test the group `(b)` and if the group doesn't match test the token `c`.
|
|
|
|
**note: The OR work at token level! It doesn't work at concatenation level!**
|
|
|
|
A query string like `abc|bde` is not equal to `(abc)|(bde)`!! The OR work only on `c|b` not at char concatenation level.
|
|
|
|
### Groups
|
|
|
|
Groups are a method to create complex patterns with repetition of blocks of tokens.
|
|
|
|
The groups are delimited by round brackets `( )`, groups can be nested and can have a quantifier as all the tokens.
|
|
|
|
`c(pa)+z` match `cpapaz` or `cpaz` or `cpapapaz` .
|
|
|
|
`(c(pa)+z ?)+` match `cpaz cpapaz cpapapaz` or `cpapaz`
|
|
|
|
let analyze this last case, first we have the group `#0` that are the most outer round brackets `(...)+`, this group has a quantifier that say to match its content at least one time `+`.
|
|
|
|
After we have a simple char token `c` and a second group that is the number `#1` :`(pa)+`, this group try to match the sequence `pa` at least one time as specified by the `+` quantifier.
|
|
|
|
After, we have another simple token `z` and another simple token ` ?` that is the space char (ascii code 32) followed by the `?` quantifier that say to capture the space char 0 or 1 time.
|
|
|
|
This explain because the `(c(pa)+z ?)+` query string can match `cpaz cpapaz cpapapaz` .
|
|
|
|
In this implementation the groups are "capture groups", it means that the last temporal result for each group can be retrieved from the `RE` struct.
|
|
|
|
The "capture groups" are store as couple of index in the field `groups` that is an `[]int` inside the `RE` struct.
|
|
|
|
**example:**
|
|
|
|
```v
|
|
text := "cpaz cpapaz cpapapaz"
|
|
query:= r"(c(pa)+z ?)+"
|
|
re, _, _ := regex.regex(query)
|
|
|
|
println(re.get_query())
|
|
// #0(c#1(pa)+z ?)+ // #0 and #1 are the ids of the groups, are shown if re.debug is 1 or 2
|
|
|
|
start, end := re.match_string(text)
|
|
// [start=0, end=20] match => [cpaz cpapaz cpapapaz]
|
|
|
|
mut gi := 0
|
|
for gi < re.groups.len {
|
|
if re.groups[gi] >= 0 {
|
|
println("${gi/2} :[${text[re.groups[gi]..re.groups[gi+1]]}]")
|
|
}
|
|
gi += 2
|
|
}
|
|
// groups captured
|
|
// 0 :[cpapapaz]
|
|
// 1 :[pa]
|
|
|
|
|
|
```
|
|
|
|
**note:** *to show the `group id number` in the result of the `get_query()` the flag `debug` of the RE object must be `1` or `2`*
|
|
|
|
### Groups Continuous saving
|
|
|
|
In particular situations it is useful have a continuous save of the groups, this is possible initializing the saving array field in `RE` struct: `group_csave`.
|
|
|
|
This feature allow to collect data in a continuous way.
|
|
|
|
In the example we pass a text followed by a integer list that we want collect.
|
|
To achieve this task we can use the continuous saving of the group that save each captured group in a array that we set with: `re.group_csave = [-1].repeat(3*20+1)`.
|
|
|
|
The array will be filled with the following logic:
|
|
|
|
`re.group_csave[0]` number of total saved records
|
|
|
|
`re.group_csave[1+n*3]` id of the saved group
|
|
`re.group_csave[1+n*3]` start index in the source string of the saved group
|
|
`re.group_csave[1+n*3]` end index in the source string of the saved group
|
|
|
|
The regex save until finish or found that the array have no space. If the space ends no error is raised, further records will not be saved.
|
|
|
|
```v
|
|
fn example2() {
|
|
test_regex()
|
|
|
|
text := "tst: 01,23,45 ,56, 78"
|
|
query:= r".*:(\s*\d+[\s,]*)+"
|
|
|
|
mut re := regex.new_regex()
|
|
//re.debug = 2
|
|
re.group_csave = [-1].repeat(3*20+1) // we expect max 20 records
|
|
|
|
re_err, err_pos := re.compile(query)
|
|
if re_err == regex.COMPILE_OK {
|
|
q_str := re.get_query()
|
|
println("Query: $q_str")
|
|
|
|
start, end := re.match_string(text)
|
|
if start < 0 {
|
|
println("ERROR : ${re.get_parse_error_string(start)}, $start")
|
|
} else {
|
|
println("found in [$start, $end] => [${text[start..end]}]")
|
|
}
|
|
|
|
// groups capture
|
|
mut gi := 0
|
|
for gi < re.groups.len {
|
|
if re.groups[gi] >= 0 {
|
|
println("${gi/2} ${re.groups[gi]},${re.groups[gi+1]} :[${text[re.groups[gi]..re.groups[gi+1]]}]")
|
|
}
|
|
gi += 2
|
|
}
|
|
|
|
// continuous saving
|
|
gi = 0
|
|
println("num: ${re.group_csave[0]}")
|
|
for gi < re.group_csave[0] {
|
|
id := re.group_csave[1+gi*3]
|
|
st := re.group_csave[1+gi*3+1]
|
|
en := re.group_csave[1+gi*3+2]
|
|
println("cg id: ${id} [${st}, ${en}] => [${text[st..en]}]")
|
|
gi++
|
|
}
|
|
} else {
|
|
println("query: $query")
|
|
lc := "-".repeat(err_pos)
|
|
println("err : $lc^")
|
|
err_str := re.get_parse_error_string(re_err)
|
|
println("ERROR: $err_str")
|
|
}
|
|
}
|
|
```
|
|
|
|
The output will be:
|
|
|
|
```
|
|
Query: .*:(\s*\d+[\s,]*)+
|
|
found in [0, 21] => [tst: 01,23,45 ,56, 78]
|
|
0 19,21 :[78]
|
|
num: 5
|
|
cg id: 0 [4, 8] => [ 01,]
|
|
cg id: 0 [8, 11] => [23,]
|
|
cg id: 0 [11, 15] => [45 ,]
|
|
cg id: 0 [15, 19] => [56, ]
|
|
cg id: 0 [19, 21] => [78]
|
|
```
|
|
|
|
## Flags
|
|
|
|
It is possible to set some flags in the regex parser that change the behavior of the parser itself.
|
|
|
|
```v
|
|
// example of flag settings
|
|
mut re := regex.new_regex()
|
|
re.flag = regex.F_BIN
|
|
|
|
```
|
|
|
|
- `F_BIN`: parse a string as bytes, utf-8 management disabled.
|
|
|
|
- `F_EFM`: exit on the first char match in the query, used by the find function.
|
|
- `F_MS`: match only if the index of the start match is 0, same as `^` at the start of the query string.
|
|
- `F_ME`: match only if the end index of the match is the last char of the input string, same as `$` end of query string.
|
|
- `F_NL`: stop the matching if found a new line char `\n` or `\r`
|
|
|
|
## Functions
|
|
|
|
### Initializer
|
|
|
|
These functions are helper that create the `RE` struct, a `RE` struct can be created manually if you needed.
|
|
|
|
#### **Simplified initializer**
|
|
|
|
```v
|
|
// regex create a regex object from the query string and compile it
|
|
pub fn regex(in_query string) (RE,int,int)
|
|
```
|
|
|
|
#### **Base initializer**
|
|
|
|
```v
|
|
// new_regex create a REgex of small size, usually sufficient for ordinary use
|
|
pub fn new_regex() RE
|
|
|
|
// new_regex_by_size create a REgex of large size, mult specify the scale factor of the memory that will be allocated
|
|
pub fn new_regex_by_size(mult int) RE
|
|
```
|
|
After a base initializer is used, the regex expression must be compiled with:
|
|
```v
|
|
// compile return (return code, index) where index is the index of the error in the query string if return code is an error code
|
|
pub fn (re mut RE) compile(in_txt string) (int,int)
|
|
```
|
|
|
|
### Operative Functions
|
|
|
|
These are the operative functions
|
|
|
|
```v
|
|
// match_string try to match the input string, return start and end index if found else start is -1
|
|
pub fn (re mut RE) match_string(in_txt string) (int,int)
|
|
|
|
// find try to find the first match in the input string, return start and end index if found else start is -1
|
|
pub fn (re mut RE) find(in_txt string) (int,int)
|
|
|
|
// find_all find all the "non overlapping" occurrences of the matching pattern, return a list of start end indexes
|
|
pub fn (re mut RE) find_all(in_txt string) []int
|
|
|
|
// replace return a string where the matches are replaced with the replace string, only non overlapped matches are used
|
|
pub fn (re mut RE) replace(in_txt string, repl string) string
|
|
```
|
|
|
|
## Debugging
|
|
|
|
This module has few small utilities to help the writing of regex expressions.
|
|
|
|
### **Syntax errors highlight**
|
|
|
|
the following example code show how to visualize the syntax errors in the compilation phase:
|
|
|
|
```v
|
|
query:= r"ciao da ab[ab-]" // there is an error, a range not closed!!
|
|
mut re := new_regex()
|
|
|
|
// re_err ==> is the return value, if < 0 it is an error
|
|
// re_pos ==> if re_err < 0, re_pos is the error index in the query string
|
|
re_err, err_pos := re.compile(query)
|
|
|
|
// print the error if one happen
|
|
if re_err != COMPILE_OK {
|
|
println("query: $query")
|
|
lc := "-".repeat(err_pos)
|
|
println("err : $lc^")
|
|
err_str := re.get_parse_error_string(re_err) // get the error string
|
|
println("ERROR: $err_str")
|
|
}
|
|
|
|
// output!!
|
|
|
|
//query: ciao da ab[ab-]
|
|
//err : ----------^
|
|
//ERROR: ERR_SYNTAX_ERROR
|
|
|
|
```
|
|
|
|
### **Compiled code**
|
|
|
|
It is possible view the compiled code calling the function `get_query()` the result will be something like this:
|
|
|
|
```
|
|
========================================
|
|
v RegEx compiler v 0.9c output:
|
|
PC: 0 ist: 7fffffff [a] query_ch { 1, 1}
|
|
PC: 1 ist: 7fffffff [b] query_ch { 1,MAX}
|
|
PC: 2 ist: 88000000 PROG_END { 0, 0}
|
|
========================================
|
|
```
|
|
|
|
`PC`:`int` is the program counter or step of execution, each single step is a token.
|
|
|
|
`ist`:`hex` is the token instruction id.
|
|
|
|
`[a]` is the char used by the token.
|
|
|
|
`query_ch` is the type of token.
|
|
|
|
`{m,n}` is the quantifier, the greedy off flag `?` will be showed if present in the token
|
|
|
|
### **Log debug**
|
|
|
|
The log debugger allow to print the status of the regex parser when the parser is running.
|
|
|
|
It is possible to have two different level of debug: 1 is normal while 2 is verbose.
|
|
|
|
here an example:
|
|
|
|
*normal*
|
|
|
|
list only the token instruction with their values
|
|
|
|
```
|
|
// re.flag = 1 // log level normal
|
|
flags: 00000000
|
|
# 2 s: ist_load PC: 0=>7fffffff i,ch,len:[ 0,'a',1] f.m:[ -1, -1] query_ch: [a]{1,1}:0 (#-1)
|
|
# 5 s: ist_load PC: 1=>7fffffff i,ch,len:[ 1,'b',1] f.m:[ 0, 0] query_ch: [b]{2,3}:0? (#-1)
|
|
# 7 s: ist_load PC: 1=>7fffffff i,ch,len:[ 2,'b',1] f.m:[ 0, 1] query_ch: [b]{2,3}:1? (#-1)
|
|
# 10 PROG_END
|
|
```
|
|
|
|
*verbose*
|
|
|
|
list all the instructions and states of the parser
|
|
|
|
```
|
|
flags: 00000000
|
|
# 0 s: start PC: NA
|
|
# 1 s: ist_next PC: NA
|
|
# 2 s: ist_load PC: 0=>7fffffff i,ch,len:[ 0,'a',1] f.m:[ -1, -1] query_ch: [a]{1,1}:0 (#-1)
|
|
# 3 s: ist_quant_p PC: 0=>7fffffff i,ch,len:[ 1,'b',1] f.m:[ 0, 0] query_ch: [a]{1,1}:1 (#-1)
|
|
# 4 s: ist_next PC: NA
|
|
# 5 s: ist_load PC: 1=>7fffffff i,ch,len:[ 1,'b',1] f.m:[ 0, 0] query_ch: [b]{2,3}:0? (#-1)
|
|
# 6 s: ist_quant_p PC: 1=>7fffffff i,ch,len:[ 2,'b',1] f.m:[ 0, 1] query_ch: [b]{2,3}:1? (#-1)
|
|
# 7 s: ist_load PC: 1=>7fffffff i,ch,len:[ 2,'b',1] f.m:[ 0, 1] query_ch: [b]{2,3}:1? (#-1)
|
|
# 8 s: ist_quant_p PC: 1=>7fffffff i,ch,len:[ 3,'b',1] f.m:[ 0, 2] query_ch: [b]{2,3}:2? (#-1)
|
|
# 9 s: ist_next PC: NA
|
|
# 10 PROG_END
|
|
# 11 PROG_END
|
|
```
|
|
|
|
the columns have the following meaning:
|
|
|
|
`# 2` number of actual steps from the start of parsing
|
|
|
|
`s: ist_next` state of the present step
|
|
|
|
`PC: 1` program counter of the step
|
|
|
|
`=>7fffffff ` hex code of the instruction
|
|
|
|
`i,ch,len:[ 0,'a',1]` `i` index in the source string, `ch` the char parsed, `len` the length in byte of the char parsed
|
|
|
|
`f.m:[ 0, 1]` `f` index of the first match in the source string, `m` index that is actual matching
|
|
|
|
`query_ch: [b]` token in use and its char
|
|
|
|
`{2,3}:1?` quantifier `{min,max}`, `:1` is the actual counter of repetition, `?` is the greedy off flag if present
|
|
|
|
### **Custom Logger output**
|
|
|
|
The debug functions output uses the `stdout` as default, it is possible to provide an alternative output setting a custom output function:
|
|
|
|
```v
|
|
// custom print function, the input will be the regex debug string
|
|
fn custom_print(txt string) {
|
|
println("my log: $txt")
|
|
}
|
|
|
|
mut re := new_regex()
|
|
re.log_func = custom_print // every debug output from now will call this function
|
|
|
|
```
|
|
|
|
## Example code
|
|
|
|
Here there is a simple code to perform some basically match of strings
|
|
|
|
```v
|
|
struct TestObj {
|
|
source string // source string to parse
|
|
query string // regex query string
|
|
s int // expected match start index
|
|
e int // expected match end index
|
|
}
|
|
const (
|
|
tests = [
|
|
TestObj{"this is a good.",r"this (\w+) a",0,9},
|
|
TestObj{"this,these,those. over",r"(th[eio]se?[,. ])+",0,17},
|
|
TestObj{"test1@post.pip.com, pera",r"[\w]+@([\w]+\.)+\w+",0,18},
|
|
TestObj{"cpapaz ole. pippo,",r".*c.+ole.*pi",0,14},
|
|
TestObj{"adce aabe",r"(a(ab)+)|(a(dc)+)e",0,4},
|
|
]
|
|
)
|
|
|
|
fn example() {
|
|
for c,tst in tests {
|
|
mut re := regex.new_regex()
|
|
re_err, err_pos := re.compile(tst.query)
|
|
if re_err == regex.COMPILE_OK {
|
|
|
|
// print the query parsed with the groups ids
|
|
re.debug = 1 // set debug on at minimum level
|
|
println("#${c:2d} query parsed: ${re.get_query()}")
|
|
re.debug = 0
|
|
|
|
// do the match
|
|
start, end := re.match_string(tst.source)
|
|
if start >= 0 && end > start {
|
|
println("#${c:2d} found in: [$start, $end] => [${tst.source[start..end]}]")
|
|
}
|
|
|
|
// print the groups
|
|
mut gi := 0
|
|
for gi < re.groups.len {
|
|
if re.groups[gi] >= 0 {
|
|
println("group ${gi/2:2d} :[${tst.source[re.groups[gi]..re.groups[gi+1]]}]")
|
|
}
|
|
gi += 2
|
|
}
|
|
println("")
|
|
} else {
|
|
// print the compile error
|
|
println("query: $tst.query")
|
|
lc := "-".repeat(err_pos-1)
|
|
println("err : $lc^")
|
|
err_str := re.get_parse_error_string(re_err)
|
|
println("ERROR: $err_str")
|
|
}
|
|
}
|
|
}
|
|
|
|
fn main() {
|
|
example()
|
|
}
|
|
```
|
|
|
|
more example code is available in the test code for the `regex` module `vlib\regex\regex_test.v`.
|
|
|