# read: analogously to write, support reading from in-memory streams in # addition to file descriptors. # # We can pass it either a file descriptor or an address to a stream. If a # file descriptor is passed in, we _read from it using the right syscall. If a # stream is passed in (a fake file descriptor), we read from it instead. This # lets us initialize input for tests. # # A little counter-intuitively, the output of 'read' ends up in.. a stream. So # tests end up doing a redundant copy. Why? Well, consider the alternatives: # # a) Reading into a string, and returning a pointer to the end of the read # region, or a count of bytes written. Now this count or end pointer must be # managed separately by the caller, which can be error-prone. # # b) Having 'read' return a buffer that it allocates. But there's no way to # know in advance how large to make the buffer. If you read less than the # size of the buffer you again end up needing to manage initialized vs # uninitialized memory. # # c) Creating more helpful variants like 'read-byte' or 'read-until' which # also can take a file descriptor or stream, just like 'write'. But such # primitives don't exist in the Linux kernel, so we'd be implementing them # somehow, either with more internal buffering or by making multiple # syscalls. # # Reading into a stream avoids these problems. The buffer is externally # provided and the caller has control over where it's allocated, its lifetime, # and so on. The buffer's read and write pointers are internal to it so it's # easier to keep in a consistent state. And it can now be passed directly to # helpers like 'read-byte' or 'read-until' that only need to support streams, # never file descriptors. # # Like with 'write', we assume our data segment will never begin at an address # shorter than 0x08000000, so any smaller arguments are assumed to be real # file descriptors. # # As a reminder, a stream looks like this: # write: int # index at which to write to next # read: int # index at which to read next # data: (array byte) # prefixed by size as usual == code # instruction effective address register displacement immediate # . op subop mod rm32 base index scale r32 # . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes read: # f: fd or (addr stream byte), s: (addr stream byte) -> num-bytes-read/eax: int # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # if (f < 0x08000000) return _read(f, s) # f can't be a user-mode address, so treat it as a kernel file descriptor 81 7/subop/compare 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 0x08000000/imm32 # compare *(ebp+8) 73/jump-if-addr>= $read:fake/disp8 # . . push args ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) # . . call e8/call _read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # return eb/jump $read:end/disp8 $read:fake: # otherwise, treat 'f' as a stream to scan from # . save registers 56/push-esi 57/push-edi # esi = f 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi # edi = s 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 0xc/disp8 . # copy *(ebp+12) to esi # eax = _buffer-4(out = &s->data[s->write], outend = &s->data[s->size], # in = &f->data[f->read], inend = &f->data[f->write]) # . . push &f->data[f->write] 8b/copy 0/mod/indirect 6/rm32/esi . . . 0/r32/eax . . # copy *esi to eax 8d/copy-address 1/mod/*+disp8 4/rm32/sib 6/base/esi 0/index/eax . 0/r32/eax 0xc/disp8 . # copy esi+eax+12 to eax 50/push-eax 
void parse_null_returns_null(void **state);
void parse_empty_returns_null(void **state);
void parse_space_returns_null(void **state);
void parse_cmd_no_args_returns_null(void **state);
void parse_cmd_with_space_returns_null(void **state);
void parse_cmd_with_too_few_returns_null(void **state);
void parse_cmd_with_too_many_returns_null(void **state);
void parse_cmd_one_arg(void **state);
void parse_cmd_two_args(void **state);
void parse_cmd_three_args(void **state);
void parse_cmd_three_args_with_spaces(void **state);
void parse_cmd_with_freetext(void **state);
void parse_cmd_one_arg_with_freetext(void **state);
void parse_cmd_two_args_with_freetext(void **state);
void parse_cmd_min_zero(void **state);
void parse_cmd_min_zero_with_freetext(void **state);
void parse_cmd_with_quoted(void **state);
void parse_cmd_with_quoted_and_space(void **state);
void parse_cmd_with_quoted_and_many_spaces(void **state);
void parse_cmd_with_many_quoted_and_many_spaces(void **state);
void parse_cmd_freetext_with_quoted(void **state);
void parse_cmd_freetext_with_quoted_and_space(void **state);
void parse_cmd_freetext_with_quoted_and_many_spaces(void **state);
void parse_cmd_freetext_with_many_quoted_and_many_spaces(void **state);
void parse_cmd_with_quoted_freetext(void **state);
void parse_cmd_with_third_arg_quoted_0_min_3_max(void **state);
void parse_cmd_with_second_arg_quoted_0_min_3_max(void **state);
void parse_cmd_with_second_and_third_arg_quoted_0_min_3_max(void **state);
void count_one_token(void **state);
void count_one_token_quoted_no_whitespace(void **state);
void count_one_token_quoted_with_whitespace(void **state);
void count_two_tokens(void **state);
void count_two_tokens_first_quoted(void **state);
void count_two_tokens_second_quoted(void **state);
void count_two_tokens_both_quoted(void **state);
void get_first_of_one(void **state);
void get_first_of_two(void **state);
void get_first_two_of_three(void **state);
void get_first_two_of_three_first_quoted(void **state);
void get_first_two_of_three_second_quoted(void **state);
void get_first_two_of_three_first_and_second_quoted(void **state);
void parse_options_when_none_returns_empty_hasmap(void **state);
void parse_options_when_opt1_no_val_sets_error(void **state);
void parse_options_when_one_returns_map(void **state);
void parse_options_when_opt2_no_val_sets_error(void **state);
void parse_options_when_two_returns_map(