Reading a file in as a number.
deltatrinity at hotmail.com
Thu Dec 11 20:10:37 CET 2003
You can read the file into a buffer, and then use mpz_import.
For example, on a x86 system, to load a 20 'unsigned long' (4-bytes or 1
unsigned long Buffer;
//... (Read 20 unsigned long from file, into Buffer)
mpz_import(Value,20,-1,sizeof(Buffer), -1, 0, Buffer);
//param 1: The mpz_t struct to fill
//Param 2: The number of 'words' (20 here). Note that 'words' here is
not to be confused with the x86 standard denomination of a 16-bit unsigned
value (WORD). This can by any arbitary size, which get converted down to
limbs by GMP.
//Param 3: Order (-1 for lowest word first)
//Param 4: Word size in bytes (size of a 'word'. In this case, the size
in byte of a single element of the buffer).
//Param 5: Endian. On x86, the first byte of each words, that is, the
byte at the lowest address, is the least significant byte. (-1 for least
significant byte first)
//Param 6: Nails. On some systems, some arithmetics/logic operations can
only be done in the lower bits of that system word. For example, where on
such system, a word size would be 32 bits, some operations can only be done
on the lowest 16 bits. So, only 2 bytes out of 4 are used by GMP for
achieving faster operations, the other are unused. On x86 architecture,
this limitation does not apply as the processor ALU can operate on all bits
of a word. (0 meen use all bits).
>From: Ernst Berg <ernst_berg at sbcglobal.net>
>To: gmp-discuss at swox.com
>Subject: Reading a file in as a number.
>Date: Thu, 11 Dec 2003 02:19:09 -0800 (PST)
> C programming is my hobby and I must admit I am still
> I'm the kind of programmer that doesn't look too deep
>into how a function works and often I use examples to
>aid me in writing programs.
> I need to understand how I would load a file into a
>number in gmp. I figure I would, maybe, use the
>Function: size_t mpz_inp_str (mpz_t rop, FILE *stream,
> My request is to see an example of how to read in a
>binary file into a gmp variable such as type mpz_t.
> If you can share an example of reading a plain binary
>file into a variable such as mpz_t I thank you.
> If there is a web site or a FAQ I should read please
>tell me as well.
>My Email is ernst_berg at sbcglobal.net
>gmp-discuss mailing list
>gmp-discuss at swox.com
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