[ovs-dev] [PATCH] json: Correct position tracking in JSON parser.

[Ethan Jackson]

Looks good.

Was there a specific issue that this fixes, or did you just happen to notice it?

Ethan

On Wed, Apr 25, 2012 at 15:38, Ben Pfaff <blp at nicira.com> wrote:
> When json_lex_input() returns false, the parser does not consume the byte
> passed in.  That byte will get processed again in the next iteration of
> the json_parser_feed() loop.  Therefore, until now, this code has
> double-counted bytes that cause a false return from json_lex_input().
>
> This fixes the problem.  Every input byte is now counted only once.
>
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  lib/json.c         |   15 +++++++--------
>  python/ovs/json.py |   20 +++++++++++---------
>  tests/ovsdb-log.at |    2 +-
>  3 files changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/lib/json.c b/lib/json.c
> index 37bdece..d514a90 100644
> --- a/lib/json.c
> +++ b/lib/json.c
> @@ -908,14 +908,6 @@ json_lex_input(struct json_parser *p, unsigned char c)
>  {
>     struct json_token token;
>
> -    p->byte_number++;
> -    if (c == '\n') {
> -        p->column_number = 0;
> -        p->line_number++;
> -    } else {
> -        p->column_number++;
> -    }
> -
>     switch (p->lex_state) {
>     case JSON_LEX_START:
>         switch (c) {
> @@ -1092,6 +1084,13 @@ json_parser_feed(struct json_parser *p, const char *input, size_t n)
>     size_t i;
>     for (i = 0; !p->done && i < n; ) {
>         if (json_lex_input(p, input[i])) {
> +            p->byte_number++;
> +            if (input[i] == '\n') {
> +                p->column_number = 0;
> +                p->line_number++;
> +            } else {
> +                p->column_number++;
> +            }
>             i++;
>         }
>     }
> diff --git a/python/ovs/json.py b/python/ovs/json.py
> index 417d231..fa5fd15 100644
> --- a/python/ovs/json.py
> +++ b/python/ovs/json.py
> @@ -1,4 +1,4 @@
> -# Copyright (c) 2010, 2011 Nicira Networks
> +# Copyright (c) 2010, 2011, 2012 Nicira Networks
>  #
>  # Licensed under the Apache License, Version 2.0 (the "License");
>  # you may not use this file except in compliance with the License.
> @@ -420,13 +420,6 @@ class Parser(object):
>         return True
>
>     def __lex_input(self, c):
> -        self.byte_number += 1
> -        if c == '\n':
> -            self.column_number = 0
> -            self.line_number += 1
> -        else:
> -            self.column_number += 1
> -
>         eat = self.lex_state(self, c)
>         assert eat is True or eat is False
>         return eat
> @@ -557,7 +550,16 @@ class Parser(object):
>         while True:
>             if self.done or i >= len(s):
>                 return i
> -            if self.__lex_input(s[i]):
> +
> +            c = s[i]
> +            if self.__lex_input(c):
> +                self.byte_number += 1
> +                if c == '\n':
> +                    self.column_number = 0
> +                    self.line_number += 1
> +                else:
> +                    self.column_number += 1
> +
>                 i += 1
>
>     def is_done(self):
> diff --git a/tests/ovsdb-log.at b/tests/ovsdb-log.at
> index bd06110..055dc70 100644
> --- a/tests/ovsdb-log.at
> +++ b/tests/ovsdb-log.at
> @@ -266,7 +266,7 @@ AT_CHECK(
>  file: read: [0]
>  file: read: [1]
>  file: read: [2]
> -file: read failed: syntax error: file: 5 bytes starting at offset 228 are not valid JSON (line 1, column 0, byte 5: syntax error at beginning of input)
> +file: read failed: syntax error: file: 5 bytes starting at offset 228 are not valid JSON (line 0, column 4, byte 4: syntax error at beginning of input)
>  file: write:["replacement data"] successful
>  ]], [ignore])
>  AT_CHECK(
> --
> 1.7.2.5
>
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