pt_json.c

#include "pt_json.h"
#include "percona_pg_telemetry.h"

#include <sys/stat.h>

/* Local functions */
static char *json_fix_value(char *str);

/*
 * Fixes a JSON string to avoid malformation of a json value. Returns
 * a palloced string that caller must pfree.
 */
char *
json_fix_value(char *str)
{
    int i;
    int len;
    int maxlen;
    char *str_escaped;
    char *s;

    if (str == NULL)
        return NULL;

    len = strlen(str);
    maxlen = (len > 0) ? len * 2 : 1;

    /* Max we'd need twice the space. */
    str_escaped = (char *) palloc(maxlen);
    s = str_escaped;

    for(i = 0; i < len; i++)
    {
        if (str[i] == '"' || str[i] == '\\')
        {
            *s++ = '\\';
            *s++ = str[i];

            continue;
        }

        *s++ = str[i];
    }

    /* Ensure that we always end up with a string value. */
    *s = '\0';

    return str_escaped;
}

/*
 * Construct a JSON block for writing.
 *
 * NOTE: We are not escape any quote characters in key or value strings, as
 * we don't expect to encounter that in extension names.
 */
char *
construct_json_block(char *msg_block, size_t msg_block_sz, char *key, char *raw_value, int flags, int *json_file_indent)
{
    char *value = NULL;
    char msg[2048] = {0};
    char msg_json[2048] = {0};

    /* Make the string empty so that we can always concat. */
    msg_block[0] = '\0';

    if (raw_value)
        value = json_fix_value(raw_value);

    if (flags & PT_JSON_BLOCK_START)
    {
        PT_FORMAT_JSON(msg_json, sizeof(msg_json), "{", (*json_file_indent));
        strlcpy(msg_block, msg_json, msg_block_sz);

        (*json_file_indent)++;
    }

    if (flags & PT_JSON_KEY_VALUE_PAIR)
    {
        snprintf(msg, sizeof(msg), "\"%s\": \"%s\",", key, value);
        PT_FORMAT_JSON(msg_json, sizeof(msg_json), msg, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);
    }

    if (flags & PT_JSON_BLOCK_KEY)
    {
        snprintf(msg, sizeof(msg), "\"key\": \"%s\",", key);
        PT_FORMAT_JSON(msg_json, sizeof(msg_json), msg, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);
    }

    if (flags & PT_JSON_BLOCK_VALUE)
    {
        snprintf(msg, sizeof(msg), "\"value\": \"%s\"", value);
        PT_FORMAT_JSON(msg_json, sizeof(msg_json), msg, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);
    }

    if (flags & PT_JSON_ARRAY_START)
    {
        if (value && value[0] != '\0')
            snprintf(msg, sizeof(msg), "\"%s\": [", value);
        else
            snprintf(msg, sizeof(msg), "\"value\": [");

        PT_FORMAT_JSON(msg_json, sizeof(msg_json), msg, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);

        (*json_file_indent)++;
    }

    /* Value is not an array so we can close the block. */
    if (flags & PT_JSON_ARRAY_END)
    {
        char closing[3] = {']', ',', '\0'};

        if (flags & PT_JSON_BLOCK_LAST)
        {
            /* Let's remove the comma in case this is the last block. */
            closing[1] = '\0';
        }

        (*json_file_indent)--;

        PT_FORMAT_JSON(msg_json, sizeof(msg_json), closing, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);
    }

    /* Value is not an array so we can close the block. */
    if (flags & PT_JSON_BLOCK_END)
    {
        char closing[3] = {'}', ',', '\0'};

        if (flags & PT_JSON_BLOCK_LAST)
        {
            /* Let's remove the comma in case this is the last block. */
            closing[1] = '\0';
        }

        (*json_file_indent)--;

        PT_FORMAT_JSON(msg_json, sizeof(msg_json), closing, (*json_file_indent));
        strlcat(msg_block, msg_json, msg_block_sz);
    }

    if (value)
        pfree(value);

    return msg_block;
}

/*
 * Open a file in the given mode.
 */
FILE *
json_file_open(char *pathname, char *mode)
{
    FILE *fp;

    fp = fopen(pathname, mode);
    if (fp == NULL)
	{
        ereport(LOG,
                (errcode_for_file_access(),
                 errmsg("Could not open file %s for writing.", pathname)));
        PT_WORKER_EXIT(PT_FILE_ERROR);
    }

    return fp;
}

/*
 * Write JSON to file.
 */
void
write_json_to_file(FILE *fp, char *json_str)
{
    int len;
    int bytes_written;

    len = strlen(json_str);
    bytes_written = fwrite(json_str, 1, len, fp);

    if (len != bytes_written)
    {
        ereport(LOG,
                (errcode_for_file_access(),
                 errmsg("Could not write to json file.")));

        fclose(fp);
        PT_WORKER_EXIT(PT_FILE_ERROR);
    }
}