Programming Forums > Application Development > C++

zedoo · Nov 30th, 2004, 7:35 AM

hi,

i am trying to read one byte of data from a FILE* like this.

int a = fread((void *)(&(col.r)), sizeof(char), 1, f_origin);

where col.r is a char. fread returns 1, so i suppose the data is read correctly into col.r

1. is this cast to (void *) necessary? could i just write

int a = fread((&(col.r)), sizeof(char), 1, f_origin); ?

2. i am struggling to find an appropriate call to printf to display the char value, for example in hexadecimal or integer. this should be easy..

thanks for your kind answers.

Eggbert · Nov 30th, 2004, 10:00 AM

>1. is this cast to (void *) necessary?
No.

>2. i am struggling to find an appropriate call to printf to display the char value, for example in hexadecimal or integer.

(Toggle Plain Text)

printf ( "Decimal: %d\nOctal: %o\nHexadecimal: %x\n", col.r, col.r, col.r );

zedoo · Nov 30th, 2004, 12:56 PM

so i can use a char wherever i can use ints?

i thought with %d has to follow an int.

felix

andersRson · Nov 30th, 2004, 2:04 PM

Quote:

Originally posted by zedoo@Nov 30 2004, 06:56 PM
i thought with %d has to follow an int.

No, if you use %d with a char you get the ascii-value.

Eggbert · Dec 4th, 2004, 8:41 AM

>so i can use a char wherever i can use ints?
>i thought with %d has to follow an int.
char is an integral type with a safe conversion to int. The inverse may not be safe, so be careful when treating int like char.

>No, if you use %d with a char you get the ascii-value.
You get the integral value. Not all systems use ASCII.

Nov 30th, 2004, 10:00 AM	#2
Eggbert Professional Programmer Join Date: Nov 2004 Posts: 250 Rep Power: 4	>1. is this cast to (void *) necessary? No. >2. i am struggling to find an appropriate call to printf to display the char value, for example in hexadecimal or integer. (Toggle Plain Text) printf ( "Decimal: %d\nOctal: %o\nHexadecimal: %x\n", col.r, col.r, col.r ); printf ( "Decimal: %d\nOctal: %o\nHexadecimal: %x\n", col.r, col.r, col.r );

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Nov 30th, 2004, 7:35 AM	#1
zedoo Newbie Join Date: Nov 2004 Posts: 2 Rep Power: 0	hi, i am trying to read one byte of data from a FILE* like this. int a = fread((void )(&(col.r)), sizeof(char), 1, f_origin); where col.r is a char. fread returns 1, so i suppose the data is read correctly into col.r 1. is this cast to (void ) necessary? could i just write int a = fread((&(col.r)), sizeof(char), 1, f_origin); ? 2. i am struggling to find an appropriate call to printf to display the char value, for example in hexadecimal or integer. this should be easy.. thanks for your kind answers.

Nov 30th, 2004, 12:56 PM	#3
zedoo Newbie Join Date: Nov 2004 Posts: 2 Rep Power: 0	so i can use a char wherever i can use ints? i thought with %d has to follow an int. felix

Dec 4th, 2004, 8:41 AM	#5
Eggbert Professional Programmer Join Date: Nov 2004 Posts: 250 Rep Power: 4	>so i can use a char wherever i can use ints? >i thought with %d has to follow an int. char is an integral type with a safe conversion to int. The inverse may not be safe, so be careful when treating int like char. >No, if you use %d with a char you get the ascii-value. You get the integral value. Not all systems use ASCII.

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Programming Forums > Application Development > C++

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