[PATCH 2 of 2 RFC] c-hglib: hg_log() level 1 function

[Idan Kamara]

On Mon, Aug 19, 2013 at 3:10 PM, Giovanni Gherdovich <g.gherdovich at gmail.com
> wrote:

>
>
> 2013/8/18 Iulian Stana <julian.stana at gmail.com>
>
>> # HG changeset patch
>> # User Iulian Stana <julian.stana at gmail.com>
>> # Date 1376828454 -10800
>> #      Sun Aug 18 15:20:54 2013 +0300
>> # Node ID 04bf311c99b8f4cf4c3e2096b493ee126f861b99
>> # Parent  21be7b973803e02b0bb310465691f88705a2dd53
>> c-hglib: hg_log() level 1 function
>>
>> The revision history could have a huge mass of data. To deal with this
>> issue, I
>> had created a iterator-like mechanism. In this way I will get the
>> changesets in
>> chunks or more-like one at the time.
>>
>> The hg_log function will prepare the command and then will call
>> cmd-server for
>> changesets. This function will return to the user a iterator structure,
>> to be
>> used on hg_fetch_log_entry funciton. (The log command will not passing any
>> changeset to the user)
>>
>> The hg_fetch_log_entry function will read changesets from command server
>> and
>> will pass into the hg_log_entry_t structure in a parse way the changeset.
>> The hg_log_entry_t structure will be one of the function parameter.
>>
>> In the main.c file it can be found an example on how this function can be
>> used.
>>
>> diff --git a/client.c b/client.c
>> new file mode 100644
>> --- /dev/null
>> +++ b/client.c
>> @@ -0,0 +1,134 @@
>> +#define _GNU_SOURCE
>> +#include <errno.h>
>> +#include <fcntl.h>
>> +#include <stdlib.h>
>> +#include <stdio.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +#include <sys/types.h>
>> +#include <sys/wait.h>
>> +#include <signal.h>
>> +
>> +
>> +#include "client.h"
>> +#include "utils.h"
>> +
>> +#define HGPATH "hg"
>> +#define CHANGESET
>> "{rev}\\0{node}\\0{tags}\\0{branch}\\0{author}\\0{desc}\
>> +                                               \\0{date|isodate}\\0"
>> +
>> +/**
>> + * \brief A helper for building the command arguments.
>> + * \param command The name for mercurial command.
>> + * \param options An array pointer to command option list.
>> + * \param template Template to be used for this command.
>> + * \retval new_string An array of pointers, where the command it's
>> almost ready
>> + *                    to be send to mercurial cmdserver.
>> + * */
>> +char **cmdbuilder(char *command, char *options[], char *template)
>> +{
>> +       int cmd_size, size;
>> +       char **new_cmd;
>> +       char *temp = "--template";
>> +
>> +       for(size = 0; options[size] != NULL; size++);
>> +       cmd_size = size + 1;
>> +       new_cmd = malloc(sizeof(char *) * (cmd_size + 3));
>> +
>> +       new_cmd[0] = command;
>> +       memcpy(new_cmd + 1, options, (cmd_size - 1)  * sizeof(char *));
>> +       if(template){
>> +               new_cmd[cmd_size] = temp;
>> +               new_cmd[cmd_size + 1] = template;
>> +               new_cmd[cmd_size + 2] = NULL;
>> +       }else{
>> +               new_cmd[cmd_size] = NULL;
>> +       }
>> +
>> +       return new_cmd;
>> +}
>> +
>> +/**
>> + * \brief 'Parse a changeset'. It's more like pointing to the correct
>> position.
>> + *
>> + * The changeset could be found on buff pointer. To not duplicate the
>> data I
>> + * choose to point every log_entry field to the right position.
>> + * \param buff The pointer to the changeset.
>> + * \param le   The log_entry_t structure where the changeset will be
>> parse.
>> + * \retval 0 if successful.
>> + * */
>> +int parse_changeset(char *buff, hg_log_entry_t *le)
>> +{
>> +       /* set pointer for revision position */
>> +       le->rev = buff;
>> +
>> +       /* set pointer for node position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->node = buff;
>> +
>> +       /* set pointer for tag position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->tags = buff;
>> +
>> +       /* set pointer for branch position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->branch = buff;
>> +
>> +       /* set pointer for author position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->author = buff;
>> +
>> +       /* set pointer for description position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->desc = buff;
>> +
>> +       /* set pointer for data position */
>> +       buff = buff + strlen(buff) + 1;
>> +       le->date = buff;
>> +
>> +       return 0;
>> +}
>> +
>> +/* The high level log command for hglib API. */
>> +hg_log_iterator *hg_log(hg_handle *handle, char *option[])
>> +{
>> +       hg_log_iterator *log_iterator = malloc(sizeof(hg_log_iterator));
>> +       log_iterator->handle = handle;
>> +
>> +       log_iterator->command = cmdbuilder("log", option, CHANGESET);
>> +
>> +       if(hg_rawcommand(handle, log_iterator->command) < 0){
>> +               return NULL;
>> +       }
>> +
>> +       log_iterator->changeset = malloc(0);
>> +       return log_iterator;
>>
>
>
> What happens here is that hg_log() does not return a status code
> (with the meaning "command successfully sent"), but the hg_log_iterator
> struct instead.
>
> A status code would be desirable and idiomatic I think;
> the struct to be passed as an argument.
>
>
>
>> +}
>> +
>> +/* The iterator next step. Getting the next changeset. */
>> +int hg_fetch_log_entry(hg_log_iterator *log_iterator, hg_log_entry_t *le)
>> +{
>> +       hg_header head = hg_head(log_iterator->handle);
>> +
>> +       if(head.channel == 'r'){
>> +               free(log_iterator->command);
>> +               free(log_iterator->changeset);
>> +               int exitcode = hg_exitcode(log_iterator->handle);
>> +               free(log_iterator);
>> +               return exitcode;
>> +       }
>> +
>> +       log_iterator->changeset = realloc(log_iterator->changeset,
>> head.length);
>> +
>> +       if(read(log_iterator->handle->p_read, log_iterator->changeset,
>> +                                       head.length) < 0){
>>
>
>
> Here you are not using hg_rawread(). Please explain why.
> Level 1 functions are meant to build on top of level 0 functions.
>
> Also: you are not reading in 4096 B chunks.
>
> Also: you are assuming that all information for a given log entry
> (a revision) are retrieved in a "single shot" of the  'o' channel.
>
> You are assuming that a log revision cannot be split across two
> iteration of output on the 'o' channel.
>
> Is this assumption safe?
>

No.
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