SRC/ReadLine.c

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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include "util.h"
#include "ReadLine.h"


/* Pass in a pointer to a token list. Is freed and then set to null */
void
FreeTokens(INOUT char ***TokensPtr)
{
    assert(*TokensPtr);
    assert(**TokensPtr);

    free(**TokensPtr);          /* Free the string data */
    free(*TokensPtr);           /* Free token list */
    *TokensPtr = NULL;          /* Invalidate pointer since mem is gone */
}


/* Returns number of tokens in list. Zero if null list */
int
CountTokens(IN char **Tokens)
{
    int count = 0;

    if(NULL == Tokens)
        {
            return 0;
        };
    while(Tokens[count])
        {
            ++count;
        };
    return count;
}


/* Reads in a single line from file, splits into tokens and allocates
 * a list of tokens. Returns the an array of character arrays with the
 * final item being marked by an empty string.
 * Returns NULL on EOF
 * NB: Token list is does as two allocations, one for pointer list
 * and one for character array. Free what pointer points to and then
 * free the pointer itself */
char **
ReadLineTokens(INOUT FILE * InFile,
               INOUT int *LineNum)
{

    enum
    { BUFFSIZE = 65536 };       /* This is much more than enough */
    char Buffer[BUFFSIZE];      /* Must match BUFFSIZE */
    char *Res;
    char *Last;
    char *Cur;
    char *Dst;
    char **Tokens;
    int TokenCount;
    int Len;
    int CurToken;
    boolean InToken;

    do
        {
            /* Read the string */
            Res = fgets(Buffer, BUFFSIZE, InFile);
            if(NULL == Res)
                {
                    if(feof(InFile))
                        {
                            return NULL;        /* Return NULL on EOF */
                        }
                    else
                        {
                            printf(ERRTAG "Unexpected error reading file\n");
                            exit(1);
                        }
                }
            ++(*LineNum);

            /* Strip newline if any */
            Last = Buffer + strlen(Buffer);
            if((Last > Buffer) && ('\n' == Last[-1]))
                {
                    --Last;
                }
            if((Last > Buffer) && ('\r' == Last[-1]))
                {
                    --Last;
                }

            /* Handle continued lines */
            while((Last > Buffer) && ('\\' == Last[-1]))
                {
                    /* Strip off the backslash */
                    --Last;

                    /* Read next line by giving pointer to null-char as start for next */
                    Res = fgets(Last, (BUFFSIZE - (Last - Buffer)), InFile);
                    if(NULL == Res)
                        {
                            if(feof(InFile))
                                {
                                    return NULL;        /* Return NULL on EOF */
                                }
                            else
                                {
                                    printf(ERRTAG
                                           "Unexpected error reading file\n");
                                    exit(1);
                                }
                        }
                    ++(*LineNum);

                    /* Strip newline */
                    Last = Buffer + strlen(Buffer);
                    if((Last > Buffer) && ('\n' == Last[-1]))
                        {
                            --Last;
                        }
                    if((Last > Buffer) && ('\r' == Last[-1]))
                        {
                            --Last;
                        }
                }

            /* Strip comment if any */
            Cur = Buffer;
            while(Cur < Last)
                {
                    if('#' == *Cur)
                        {
                            Last = Cur;
                            break;
                        }
                    ++Cur;
                }

            /* Count tokens and find size */
            assert(Last < (Buffer + BUFFSIZE));
            Len = 0;
            TokenCount = 0;
            Cur = Buffer;
            InToken = FALSE;
            while(Cur < Last)
                {
                    if(InToken)
                        {
                            if((' ' == *Cur) || ('\t' == *Cur))
                                {
                                    InToken = FALSE;
                                }
                            else
                                {
                                    ++Len;
                                }
                        }
                    else
                        {
                            if((' ' != *Cur) && ('\t' != *Cur))
                                {
                                    ++TokenCount;
                                    ++Len;
                                    InToken = TRUE;
                                }
                        }
                    ++Cur;      /* Advance pointer */
                }
        }
    while(0 == TokenCount);

    /* Find the size of mem to alloc. Use a contiguous block so is 
     * easy to deallocate */
    Len = (sizeof(char) * Len) +        /* Length of actual data */
        (sizeof(char) * TokenCount);    /* Null terminators */

    /* Alloc the pointer list and data list. Count the final 
     * empty string we will use as list terminator */
    Tokens = (char **)my_malloc(sizeof(char *) * (TokenCount + 1));
    *Tokens = (char *)my_malloc(sizeof(char) * Len);

    /* Copy tokens to result */
    Cur = Buffer;
    Dst = *Tokens;
    InToken = FALSE;
    CurToken = 0;
    while(Cur < Last)
        {
            if(InToken)
                {
                    if((' ' == *Cur) || ('\t' == *Cur))
                        {
                            InToken = FALSE;
                            *Dst = '\0';        /* Null term token */
                            ++Dst;
                            ++CurToken;
                        }
                    else
                        {
                            *Dst = *Cur;        /* Copy char */
                            ++Dst;
                        }
                }
            else
                {
                    if((' ' != *Cur) && ('\t' != *Cur))
                        {
                            Tokens[CurToken] = Dst;     /* Set token start pointer */
                            *Dst = *Cur;        /* Copy char */
                            ++Dst;
                            InToken = TRUE;
                        }
                }
            ++Cur;              /* Advance pointer */
        }
    if(InToken)
        {
            *Dst = '\0';        /* Null term final token */
            ++Dst;
            ++CurToken;
        }
    assert(CurToken == TokenCount);

    /* Set the final empty string entry */
    Tokens[CurToken] = NULL;

    /* Return the string list */
    return Tokens;
}

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