read already uses buffered input, and each call to it does not make a system call.

#!/usr/bin/perl

while (read(STDIN,$buf,$ENV{BLOCKSIZE}))
{
  ;
}
[download]

produces:

$ BLOCKSIZE=1 strace -e read -c perl /tmp/t6 <zelda4rom.zip 
Called read 26968 times.
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00    0.002888         160        18           read
------ ----------- ----------- --------- --------- ----------------
100.00    0.002888                    18           total

$ BLOCKSIZE=1024 strace -e read -c perl /tmp/t6 <zelda4rom.zip 
Called read 27 times.
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00    0.000370          19        19           read
------ ----------- ----------- --------- --------- ----------------
100.00    0.000370                    19           total

$ BLOCKSIZE=4096 strace -e read -c perl /tmp/t6 <zelda4rom.zip 
Called read 7 times.
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00    0.000315          17        19           read
------ ----------- ----------- --------- --------- ----------------
100.00    0.000315                    19           total

---

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