Format converter

v2ex_545359.cc

#include<cstdio>
#include<cstdlib>
using namespace std;

/*
Example input:
    {"root1"{"item1""1""item2""abc""item3"{"cell"{"cell1"
    {"cell1Name""99"}"cell2"{"cell2Name""cdb"}}}"item4""valueI"}
    "root2"{"item1""88""item2""tg""item3"{"cell"{"cell1"{"cell1Name"
    "99"}"cell2"{"cell2Name""ujh"}}}"item4""valueb"}}

Example output:
{"root1":{"item1":"1","item2":"abc","item3":{"cell":{
"cell1":{"cell1Name":"99"},"cell2":{"cell2Name":"cdb"}}},
"item4":"valueI"},"root2":{"item1":"88","item2":"tg","item3":{"cell":{
"cell1":{"cell1Name":"99"},"cell2":{"cell2Name":"ujh"}}},"item4":"valueb"}}
*/

enum RecordStatus
{
    // Awaiting left brace
    RS_AWAIT_LB,
    // Awaiting key or right brace
    RS_AWAIT_NAME_RB,
    // Awaiting key or right brace, not the first key
    RS_AWAIT_NAME_RB_2,
    // Awaiting value
    RS_AWAIT_VALUE
};
enum StringStatus
{
    // Awaiting opening quotation mark
    SS_AWAIT_OPEN,
    // Awaiting closing quotation mark or escape sequence or literal character
    SS_AWAIT_CLOSE_ESCAPE,
    // Escaping character
    SS_ESCAPE
};

bool IsSpace(char ch)
{
    return ch == ' ' || ch == '\t' || ch == '\v' || ch == '\r' || ch == '\n';
}

bool TransformString(StringStatus status = SS_AWAIT_OPEN)
{
    int ch;
    while ((ch = getchar()) != -1)
    {
    switch (status)
    {
    case SS_AWAIT_OPEN:
        if (ch == '"')
        {
            putchar('"');
            status = SS_AWAIT_CLOSE_ESCAPE;
        }
        else if (!IsSpace(ch))
        {
            return false;
        }
        break;
    case SS_AWAIT_CLOSE_ESCAPE:
        putchar(ch);
        if (ch == '"')
            return true;
        else if (ch == '\\')
            status = SS_ESCAPE;
        break;
    case SS_ESCAPE:
        putchar(ch);
        status = SS_AWAIT_CLOSE_ESCAPE;
        break;
    default:
        return false;
    }
    }
    return false;
}

bool TransformRecord(RecordStatus status = RS_AWAIT_LB)
{
    int ch;
    while ((ch = getchar()) != -1)
    {
    switch (status)
    {
    case RS_AWAIT_LB:
        if (ch == '{')
        {
            putchar('{');
            status = RS_AWAIT_NAME_RB;
        }
        else if (!IsSpace(ch))
        {
            return false;
        }
        break;
    case RS_AWAIT_NAME_RB:
    case RS_AWAIT_NAME_RB_2:
        if (ch == '"')
        {
            if (status == RS_AWAIT_NAME_RB_2)
                putchar(',');
            putchar('"');
            if (!TransformString(SS_AWAIT_CLOSE_ESCAPE))
                return false;
            putchar(':');
            status = RS_AWAIT_VALUE;
        }
        else if (ch == '}')
        {
            putchar('}');
            return true;
        }
        else if (!IsSpace(ch))
        {
            return false;
        }
        break;
    case RS_AWAIT_VALUE:
        if (ch == '"')
        {
            putchar('"');
            if (!TransformString(SS_AWAIT_CLOSE_ESCAPE))
                return false;
            status = RS_AWAIT_NAME_RB_2;
        }
        else if (ch == '{')
        {
            putchar('{');
            if (!TransformRecord(RS_AWAIT_NAME_RB))
                return false;
            status = RS_AWAIT_NAME_RB_2;
        }
        else if (!IsSpace(ch))
        {
            return false;
        }
        break;
    default:
        return false;
    }
    }
    return false;
}

bool CheckTrailingSpaces()
{
    int ch;
    while ((ch = getchar()) != -1)
        if (!IsSpace(ch))
            return false;
    return true;
}

int main()
{
    return (TransformRecord() && CheckTrailingSpaces())
        ? EXIT_SUCCESS
        : EXIT_FAILURE;
}