hiredis , MSET using binary safe API

[nept]

Hi,
I have an array of keys and an array of values in byte:
#define  unsigned char byte;
char *key[n];
byte *value[n];
int len[2]

n is variable so I can't use this command (for example with n=2)
redisCommand(r.myRedisConnection,"MSET %b %b %b %b", key[0], (size_t) strlen(key[0]), value[0], (size_t)len[0],key[1], (size_t) strlen(key[1]), value[1], (size_t) len[1]);

Can I do it?
Thanks.

[Jan-Erik Rediger]

The easiest way would be to use `redisCommandArgv` and build up your
`argv` array, filling it with keys and values as you need it.

Rough pseudo-code:

argv = malloc(2*n+1);
argv[0] = "MSET";
for (i=0;i<n;i++) {
argv.append(key[i]);
argv.append(value[i]);
}

redisCommandArgv(ctx, 2*n+1, argv, NULL);

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[Salvatore Aurnia]

Thanks for you replay.

The problem is that the values are bytes, but **argv is **char type,
so I can't set it in argv without problem.
With memcpy I have core dump.

[Jan-Erik Rediger]

Cast it ¯\_(ツ)_/¯
You're "byte" is laos just a "unsigned char".

You'd still need to allocate the memory in the argv array itself.

[Salvatore Aurnia]

my problem is that array of byte is createdby matlab, where byte byte
is uint8, so if a byte is 0, char(0)='\0' and

the string is over.

[Jan-Erik Rediger]

Then pass in the length of these arrays using the last argument to redisCommandArgv.
hiredis can easily handle arbitrary binary data if you give it the
actual length

[Salvatore Aurnia]

it doesn't work.
if a byte is 0, nothing to do.

[Salvatore Aurnia]

the null byte is considerated as a terminator and a buffer holding
such is "truncated" at the first zero byte instance.

[Jan-Erik Rediger]

For strings and related string functions, yes.
For arbitrary binary data that can contain nul bytes, you have to keep
track of the length by yourself. Neither hiredis nor C can do that for
you.

[Salvatore Aurnia]

It's true.
But if I convert a byte array to *char[], 0 is converted to '\0' so
it's considerated as null char, so my key is not stored.

With command:

redisCommand(r.myRedisConnection,"MSET %b %b %b %b", key[0], (size_t)
strlen(key[0]), value[0], (size_t)len[0],key[1], (size_t)
strlen(key[1]), value[1], (size_t) len[1]);

I haven't problems, but I have a number of arguments, so I don't know
how to fix it.

[Jan-Erik Rediger]

Again: Neither C nor hiredis do care.
If you _explicitely_ pass the right length it doesn't matter if there
are null bytes in the data, hiredis will use the amount of bytes you
specified by the length parameter.

[Salvatore Aurnia]

"If you _explicitely_ pass the right length it doesn't matter if there
are null bytes in the data, hiredis will use the amount of bytes you
specified by the length parameter."

I try it, but it doesn't work for me.

[Salvatore Aurnia]

Sorry, I resolved it.
I used "MSET %b ... %b", where the number of '%b' is equal to size of
array, with "MSET" it works.
Thanks.