Title: STANDARD USAGE OF C LANGUAGE RECIO LIBRARY Copyright: (C) 1994 William Pierpoint Version: 2.02 Date: May 5, 1994 1.0 INTRODUCTION The implementation descibed by this standard usage is a superset of the recio specification. Enhancements are noted in the text. 1.1 Mnemonics The recio functions have been given a consistent mnemonic naming convention. All recio functions are in lower case and start with the letter r. Function names are analogous to functions. Mnemonics are as follows: Single letter (field functions) Multi-letter ---------------------------------------- ----------------- b - base (prefix) beg - beginning c - column (prefix), character (suffix) ch - character d - double (suffix) col - column f - float (suffix) cxt - context i - integer (suffix) eof - end of file l - long (suffix) err - error n - number fld - field buffer r - record pointer (first letter) fn - function s - string pointer (suffix) no - number u - unsigned (suffix) rec - record buffer siz - size of buffer str - string txt - text 1.2 Order The order in which the prefix mnemonics appear indicates the order in which the arguments appear in the function. The suffix mnemonics of the input functions tell you what the function returns. The suffix mnemonics of the output functions indicate the last argument and tell you what the function outputs. All output functions return an integer with a zero value if the function executed successfully. For example, the input function rbgetui(): arguments: r - record pointer b - base (radix) of input returns: ui - unsigned integer The output function rbputui(): arguments: r - record pointer b - base (radix) of input ui - unsigned integer is output Note: c is used in the prefix of a function's name only once even if there are two column arguments. If the function inputs or outputs a character, there is only one column argument; otherwise there are two. 2.0 ERROR AND WARNING CHECKING The functions declared in the header make use of the errno macro defined in section 4.1.3 of ANSI X3.159-1989. This mechanism was chosen because (1) the conversion functions (strtod(), strtol(), etc.) make use of this error reporting mechanism and (2) the functions make use of the conversion functions. In this implementation, errno can return the following macro constants: 0 - No error. EACCES - permission denied. EINVAL - invalid argument (usually null record pointer). EMFILE - too many open files. ENOENT - no such file or directory. ENOMEM - out of memory. Beginning with version 1.1, recio functions set errno when the record pointer is invalid and set an internal error number when the record pointer is valid. The recio error number is accessed through the rerror function. The rerror function can return the following macro constants: 0 - No error. R_EINVAL - invalid argument (not the record pointer). R_EINVDAT - invalid data. R_EINVMOD - invalid mode. R_EMISDAT - missing data. R_ENOMEM - out of memory. R_ENOPUT - unable to write data to output. R_ERANGE - data out of range. Beginning with version 2.0, recio functions set an internal warning number when the record pointer is valid. The recio library never sets the warning number when the record pointer is invalid. The recio warning number is accessed through the rwarning function. The rwarning function can return the following macro constants: 0 - No warning. R_WEMPSTR - empty data string. R_WNOREG - unable to register exit function with atexit(). R_WWIDTH - data too wide for columnar output. 2.1 Define Callback Error Function First define a callback error function to be used by the recio functions. You may give the function any name you wish. In the sample function below, the name rerrfn is used. The function takes one argument, a record pointer (REC *). It returns nothing (void). The function must first check for a valid record pointer using the risvalid function. Other than that, you can customize it to do whatever you want. The recio functions use a callback error function in order to give the most flexibility in handling errors. This rerrfn function just sends information to stderr. You may wish to send information to a printer, a file, a window, or a dialog box. You might even want to give users the ability to examine errors and enter corrections. If the error is corrected, you will want to call the rclearerr function before your callback error function returns. When your callback error function is invoked, check rerror() or errno to determine the cause of the error. Symbolic errno constants: * EACCESS means that you don't have permission to access this file. All MSDOS files have read permission. * EINVAL indicates an invalid argument to a function, usually a NULL record pointer. This resulted from a programming error. * EMFILE means the program tried to open more files than the maximum allotted by ROPEN_MAX or FOPEN_MAX. If your program is interactive, the user can close one or more open record streams. Or you might decide that ROPEN_MAX or FOPEN_MAX needs to be a larger value. * ENOENT says that ropen() could not find the requested file to open. Perhaps the name of the file was misspelled, or your program looked in wrong directory. If your program was trying to read a configuration file, it could use internal default values when the configuration file does not exist. * ENOMEM indicates that the program ran out of heap space. You may be able to correct this if you are able to deallocate memory you no longer need. For example, you could reduce the size of buffers when the size only affects speed. Such buffers need to be flushed first. Buffers used by the recio library do not fit this criteria. Symbolic rerror() constants: * R_EINVDAT says the data is invalid. Invalid data is caused by an unrecognized character in the field. For example, rgetui() doesn't expect to see a negative sign, so a negative number will be flagged as invalid data. * R_EINVMOD indicates that you opened a file in read mode, then used an output function or opened a file in write or append mode, then used an input function. * R_EMISDAT says the data is missing. Missing data means the field is empty. If you expect a number, you could substitute either zero or some unique number to indicate an empty field. * R_ENOMEM indicates that the program ran out of heap space. You may be able to correct this if you are able to deallocate memory you no longer need. For example, you could reduce the size of buffers when the size only affects speed. Such buffers need to be flushed first. Buffers used by the recio library do not fit this criteria. * R_ENOPUT says the program was unable to write the data to output. This could indicate that the disk is full. * R_ERANGE tells you that the data is outside the range of the function. For instance, suppose you used rgeti() to get an integer and the data value is 32768. If a 16-bit integer has an upper limit of 32767, the value is too large. If the data is wrong, you can have the error function correct it. If the data is right, you have to correct the data type in the program. The main purpose of this sample callback error function is to show some of kinds of things you can do in a callback error function. Note that when an error occurs, the column number indicator rcolno() has moved just beyond the error. To make it clearer to the user where the error occurred, rerrfn() displays rcolno()-1, but not less than rbegcolno(), the column number for the first column. A more detailed callback error function is given in the source code for the test program TESTCHG.C. The test program callback error function makes use of the rfix functions to fix up bad data (primarily overflows and underflows) and continue processing. If appropriate for your application, you can use these functions as well. They have been compiled into the recio libraries for your potential use. /* define callback error function */ void rerrfn(REC *rp) { /* if rp is a valid record pointer */ if (risvalid(rp)) { /* if reof indicator set */ if (reof(rp)) { fprintf(stderr, "ERROR reading %s -- " "tried to read past end of file\n\n", rnames(rp)); /* else rerror indicator set */ } else { /* determine cause of error */ switch (rerror(rp)) { /* input data errors */ case R_ERANGE: case R_EINVDAT: case R_EMISDAT: /* output data errors */ case R_ENOPUT: /* print location of error */ fprintf(stderr, "DATA ERROR in FILE %s at LINE %ld," " FIELD %u, COLUMN %u -- %s\n", rnames(rp), rrecno(rp), rfldno(rp), max(rcolno(rp)-1, rbegcolno(rp)), rerrstr(rp)); break; /* non-fatal errors */ case R_ENOREG: fprintf(stderr, "WARNING -- %s\n", rerrstr(rp)); rclearerr(); break; /* fatal errors (R_EINVMOD, R_EINVAL, R_ENOMEM) */ default: fprintf(errout, "FATAL ERROR reading FILE %s -- %s\n", rnames(rp), rerrstr(rp)); abort(); break; } } /* else invalid record pointer */ } else { switch (errno) { /* non-fatal errors */ case EACCES: case EMFILE: fprintf(errout, "WARNING: %s\n", strerror(errno)); break; /* fatal errors (EINVAL, ENOMEM) */ default: fprintf(errout, "FATAL ERROR: %s\n", strerror(errno)); abort(); break; } } } 2.2 Define Callback Warning Function Next define a callback warning function. You may give the function any name you want. In the sample function below, the name rwarnfn is used. The function takes one argument, a record pointer (REC *). It returns nothing (void). The recio functions use a callback warning function in order to give the most flexibility in handling unusual conditions. For example, the recio library considers empty data strings to be legal but your application may want to flag an empty data string as a data error. You can do that by checking for R_WEMPSTR warnings in your callback warning function. When your callback warning function is invoked, check rwarning() to determine the cause of the warning. Symbolic warning constants: * R_WEMPSTR says that an empty data string was input. If you want to substitute another string, just use the rsetfldstr function to stuff the field buffer inside your callback warning function. * R_WWIDTH indicates that on output, the data will not fit between the columns specified. If the data is numeric, the recio output functions write asterisks to the output; if the data is a string, a truncated string is written. * R_WNOREG means the program was unable to register the internal recio exit function with the ANSI atexit() function. The internal recio exit function ensures that all open record streams are closed and all dynamic memory allocated by the recio library is deallocated. You can also use your callback warning function to keep track of the number of warnings, then print a summary of any warnings just before you close a record stream. You will find an example in the test program TESTCHP.C. void rwarnfn(REC *rp) { if (risvalid(rp)) { switch (rwarning(rp)) { case R_WNOREG: /* atexit() full */ fprintf (errout, "WARNING %s\n", rwarnstr(rp)); break; case R_WEMPSTR: /* empty data string */ fprintf(errout, "WARNING reading %s at record %lu and field %u -- %s\n", rnames(rp), rrecno(rp), rfldno(rp), rwarnstr(rp)); break; case R_WWIDTH: /* data too wide for columns */ fprintf(errout, "WARNING writing %s at record %lu and field %u -- %s\n", rnames(rp), rrecno(rp), rfldno(rp), rwarnstr(rp)); break; } } } 2.3 Register Callback Error and Warning Functions Once you have written your callback error and warning functions, you must let the other recio functions know that they exist. You use the rseterrfn and rsetwarnfn functions to register your callback functions. /* register callback error and warning functions */ rseterrfn(rerrfn); rsetwarnfn(rwarnfn); 3.0 OPEN FILE 3.1 Open File and Get Record Pointer Use the ropen function to open the file you want to read, write, or append. Store the record pointer returned by the ropen function. Do not open recin, recout, recerr, or recprn (MSDOS printer). They are always open, so they do not need to be opened or closed. REC *rp = ropen("FILENAME.DAT", "r"); 3.2 Check Record Pointer Following the ropen function, you need to check to see if the file was opened correctly. If ropen returned a NULL pointer, then the file was not opened. Errors other than ENOENT are reported to your callback error function. ENOENT is not reported since you may want to use default values if the data file is not available. /* if ropen() failed */ if (!rp) { /* if it failed because file does not exist */ if (errno==ENOENT) { /* action to take when file does not exist */ ... } /* else ropen() succeeded */ } else { /* set up stream (see sections 3.3 - 3.6) */ ... /* read or write file (see sections 4 and 5) */ ... /* close file (see section 6) */ rclose(rp); } 3.3 Set Field and Text Delimiters The space character is the default value for both the field and text delimiters. The space character matches any white space. If you need to use something else, you need to explicitly set the values. Application maintenance will be easier if you always set the values. rsetfldch(rp, ','); /* set field delimiter character */ rsettxtch(rp, '"'); /* set text delimiter character */ 3.4 Set Field and Record Buffer Sizes Setting the field and record buffer sizes is optional. Buffers will be automatically reallocated as necessary. However if you set the field and record sizes in advance to the maximum value needed, you can reduce memory fragmentation. The field and record buffers are not used for output. rsetfldsiz(rp, 41); /* set size of field buffer */ rsetrecsiz(rp, 133); /* set size of record buffer */ 3.5 Set Context Number If your application opens record streams with more than one data format, you will want to set a context number. You use the context number so that your callback error function can determine (using the rcxtno function) which data format it is dealing with. Each context number must be a positive integer; zero and negative numbers are reserved. Predefined context symbolic constants are RECIN, RECOUT, RECERR, and (for MSDOS) RECPRN. #define SOILS_DB 1 #define BUILDINGS_DB 2 rsetcxtno(rp, SOILS_DB); /* set context number */ 3.6 Set Beginning Column Number The first column number in the record buffer defaults to zero. If you prefer column numbering to start at one, use the rsetbegcolno function. It is mainly useful if using column delimited data. If a number takes up the first ten columns of the record, the column numbering will be 0 to 9 if rsetbegcolno() is set to 0, or 1 to 10 is rsetbegcolno() is set to 1. rsetbegcolno(rp, 1); /* first column is column 1 */ 4.0 RECORD FUNCTIONS 4.1 The rgetrec Function If all the records in a data file have the same format, you will want to loop through all the records until the end of file is reached. If each record has a different format, you must call the rgetrec function each time you want to get the next record. Calling rgetrec() is optional for the first record. /* read all records in file */ while (rgetrec(rp)) { /* Section 5 field functions go here ... */ } 4.2 The rputrec Function After you write all the fields in one record, use the rputrec function to put the end-of-record newline character to the output and to reset the internal recio library variables for the next record. /* write end-of-record */ rputrec(rp); 4.3 The rrecs Macro To get a pointer to the start of the record buffer, use the rrecs macro. /* echo record contents to stdout */ printf("%s\n", rrecs(rp)); 4.4 The rrecno Macro To get the record number, use the rrecno macro. /* echo record number and record contents to stdout */ printf("%ld: %s\n", rrecno(rp), rrecs(rp)); 4.5 The rsetrecstr Function There may be times when you will find it useful to stuff the record buffer with your own string, then use the field input functions to scan the fields. Use the rsetrecstr function for this. 5.0 GET AND PUT FIELD DATA 5.1 Field functions There are 48 functions that can be used to read or write data. A mnemonic system makes it easy to construct the name of any function you want. All you need to remember is that there are four prefixes, two bodies, and eight suffixes, and that the rb and rcb prefixes are used only with the i, l, ui, and ul suffixes. If the prefix contains the letter 'c', it is a column delimited field function. If the prefix contains the letter 'b', it is a field function that reads or writes an integral number in a specified base (radix). The eight suffixes indicate the eight data types: character, double, float, integer, long, string, unsigned integer, and unsigned long. Prefix Body Suffix Prefix Body Suffix ------ ---- ------ ------ ---- ------ r get c rb get i rc put d rcb put l f ui i ul l s ui ul 5.2 The rskipfld Macro If your application does not need to read the data in a field, you can skip over the field by using the rskipfld macro. /* skip over a field */ if (rskipfld(rp) != 1) printf("Unable to skip field.\n"); 5.3 The rskipnfld Function If your application does not need to read the data in several adjacent fields, you can skip over the fields by using the rskipnfld function. /* skip over three fields */ if (rskipnfld(rp, 3) != 3) printf("Unable to skip 3 fields.\n"); 5.4 The reof Macro Use the reof macro to determine when the record stream has reached the end of file. /* if error or end of file reached */ while (rgetrec(rp)) { ... } /* if end of file */ if (reof(rp)) { ... /* else error */ } else { ... } 5.5 The rerror Function Use the rerror function to determine if an error has occurred on a record stream. You can access a text string for the error using the rerrstr function. if (rerror(rp)) printf("ERROR reading %s - %s\n", rnames(rp), rerrstr(rp)); rclose(rp); It is a good practice to check for any errors just before closing a record stream. If the error indicator is clear, you have additional confidence that the stream was processed correctly. 5.6 The rseterr Function If you write wrapper functions or other functions that interact with recio functions, your code will need to handle errors. If can use the rseterr function to set the error number and to call the record stream callback error function. /* get integer and validate range */ int rrgeti(REC *rp, int min, int max) { int result; result = rgeti(rp); if (result < min || result > max) { rseterr(rp, R_ERANGE); } return result; } 5.7 The rwarning Function Use the rwarning macro to determine if a warning has occurred on a record stream. if (rwarning(rp)) printf("ERROR %s - %s\n", rnames(rp), rwarnstr(rp)); It is good practice to check for any warnings just before closing an output record stream. 5.8 The rsetwarn Function If you write wrapper functions or other functions that interact with recio functions, you may need to provide warnings. The rsetwarn function sets the warning number and calls the record stream callback warning function. rsetwarn(rp, R_WWIDTH); 6.0 CLOSE FILE 6.1 Close File When finished reading or writing a data file, close it. Do not close recin, recout, recerr, or recprn as they are always open. /* close record file */ rclose(rp); 6.2 Close All Files Rather than closing record files one at a time, one can close all open record files at once using the rcloseall function. /* all done */ rcloseall(); 7.0 REFERENCES 1. ANSI X3.159-1989. American National Standard for Information Systems - Programming Language - C. American National Standards Institute, 11 West 42nd Street, New York, NY 10036, 1990. 8.0 INDEX errno macro ............ 2.0, 2.1, 3.2 rbegcolno macro ........ 2.1 rclearerr function ..... 2.1 rclose function ........ 6.1 rcloseall function ..... 6.2 rcolno macro ........... 2.1 rcxtno macro ........... 3.5 recin expression ....... 3.1, 6.1 reof macro ............. 2.1, 5.4 rerror function ........ 2.1, 5.5 rerrstr function ....... 2.1, 5.5 rfix functions ......... 2.1 rflds macro ............ 2.1 rfldno macro ........... 2.1 rbget functions ........ 5.1 rbput functions ........ 5.1 rcbget functions ....... 5.1 rcbput functions ....... 5.1 rcget functions ........ 5.1 rcput functions ........ 5.1 rget functions ......... 5.1 rgetrec function ....... 4.1 risvalid function ...... 2.1 rnames macro ........... 2.1 ropen function ........ 3.1 rput functions ......... 5.1 rrecs macro ............ 2.1, 4.3 rrecno macro ........... 2.1, 4.4 rsetbegcolno function .. 3.6 rsetcxtno function ..... 3.5 rseterr function ....... 5.6 rseterrfn function ..... 2.3 rsetfldch function ..... 3.3 rsetfldsiz function .... 3.4 rsetfldstr function .... 2.1 rsetrecsiz function .... 3.4 rsetrecstr function .... 4.5 rsettxtch function ..... 3.3 rsetwarn function ...... 5.8 rsetwarnfn function .... 2.3 rskipfld macro ........ 5.2 rskipnfld function ..... 5.3 rwarning function ...... 2.2, 5.7 rwarnstr function ...... 2.2, 5.7