Add cs_buffer. Breaking API change.

[numas13]

Remove cs_malloc() and cs_free().

cs_disasm_iter() is a tiny wrapper around cs_disasm(count=1).

Your checklist for this pull request

• I've documented or updated the documentation of every API function and struct this PR changes.
• I've added tests that prove my fix is effective or that my feature works (if possible)

Detailed description

API change unifies disassembly process. Before, there were two separate functions to disassemble one instruction at a time in a loop and many instructions into a dynamic buffer. Commit will introduce user allocatable buffer that can be used in both situations with one function.

Updating the use of cs_disasm_iter() is a little more complicated than cs_disasm():

// old api
cs_insn *insn = cs_malloc(handle);
while (cs_disasm_iter(handle, &code, &code_size, &ip, insn)) {
    disassembled_instructions += 1;
}
cs_free(insn);

Must be changed to:

// new api
cs_buffer *buffer = cs_buffer_new(1); // create buffer with 1 element
while (cs_disasm_iter(handle, &code, &code_size, &ip, buffer)) {
    cs_insn *insn = &buffer->insn[0]; // get first insn in a buffer
    disassembled_instructions += 1;
}
cs_buffer_free(buffer); // free buffer

Updating the use of cs_disasm() is straightforward, just use cs_buffer_new(0) to create a buffer and pass it to cs_disasm().

Benchmarks

❯ hyperfine -N ./orig/test_iter_benchmark ./test_iter_benchmark
Benchmark 1: ./orig/test_iter_benchmark
  Time (mean ± σ):     10.632 s ±  0.227 s    [User: 10.622 s, System: 0.004 s]
  Range (min … max):   10.327 s … 11.007 s    10 runs
 
Benchmark 2: ./test_iter_benchmark
  Time (mean ± σ):     10.815 s ±  0.082 s    [User: 10.812 s, System: 0.001 s]
  Range (min … max):   10.695 s … 10.986 s    10 runs
 
Summary
  './orig/test_iter_benchmark' ran
    1.02 ± 0.02 times faster than './test_iter_benchmark'

❯ ARGS="10 0x028800 0x1517dd libc.so"; hyperfine -N "./orig/test_file_benchmark $ARGS" "./test_file_benchmark $ARGS"
Benchmark 1: ./orig/test_file_benchmark 10 0x028800 0x1517dd libc.so
  Time (mean ± σ):      2.352 s ±  0.035 s    [User: 2.349 s, System: 0.002 s]
  Range (min … max):    2.299 s …  2.388 s    10 runs
 
Benchmark 2: ./test_file_benchmark 10 0x028800 0x1517dd libc.so
  Time (mean ± σ):      2.392 s ±  0.053 s    [User: 2.387 s, System: 0.003 s]
  Range (min … max):    2.329 s …  2.497 s    10 runs
 
Summary
  './orig/test_file_benchmark 10 0x028800 0x1517dd libc.so' ran
    1.02 ± 0.03 times faster than './test_file_benchmark 10 0x028800 0x1517dd libc.so'

Test plan

Update bindings and user software.

Closing issues

...

[Rot127]

Looks awesome! It really cleans up the API a lot. Especially internally.
Please rebase this on onto the ASAN PR from me or wait until it is merged: #2313
Just so we get extra test coverage.

@aquynh @kabeor Please take a look. I am very much in favor of this.

[numas13]

Please rebase this on onto the ASAN PR from me or wait until it is merged: #2313 Just so we get extra test coverage.

There is one problem in test_arm_regression. Is it expected?

[numas13]

I've updated python bindings and review is appreciated.

[aquynh]

please avoid breaking API

[numas13]

I'm closing PRs. We'll think about what can be done.