mirror of
https://github.com/ByteWelder/Tactility.git
synced 2026-10-17 02:45:05 +00:00
104 lines
3.0 KiB
C++
104 lines
3.0 KiB
C++
#include <coreutils/command_support.h>
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#include <app/manifest.h>
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#include <cstdio>
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#include <cstdlib>
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namespace {
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// tail keeps a ring of the last N lines, so the file is still read in one forward pass rather than
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// seeking backwards, which would be far more code for no benefit at these file sizes.
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constexpr int TAIL_MAX_LINES = 32;
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constexpr size_t TAIL_MAX_LINE_LENGTH = 200;
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struct TailState {
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char lines[TAIL_MAX_LINES][TAIL_MAX_LINE_LENGTH];
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int count;
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int next;
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size_t columnn;
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};
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bool collectTailChunk(const char* data, size_t length, void* context) {
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auto* state = static_cast<TailState*>(context);
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for (size_t i = 0; i < length; i++) {
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const char c = data[i];
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if (c == '\n') {
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state->lines[state->next][state->columnn] = '\0';
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state->next = (state->next + 1) % TAIL_MAX_LINES;
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if (state->count < TAIL_MAX_LINES) {
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state->count++;
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}
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state->columnn = 0;
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} else if (state->columnn < TAIL_MAX_LINE_LENGTH - 1) {
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const bool printable = (c == '\t') ||
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(static_cast<unsigned char>(c) >= 0x20 && static_cast<unsigned char>(c) < 0x7F);
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state->lines[state->next][state->columnn++] = printable ? c : '.';
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}
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}
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return true;
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}
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} // namespace
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namespace coreutils::tail {
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static int32_t main(int argc, char* argv[]) {
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int count = 10;
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const int first = parseLineCount(argc, argv, &count);
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if (first >= argc) {
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printf("usage: tail [-n N] <file>\n");
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return 1;
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}
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if (count > TAIL_MAX_LINES) {
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count = TAIL_MAX_LINES;
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}
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char path[FILE_MAX_PATH_STRING_LENGTH];
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if (!resolvePathArg("tail", argv[first], path, sizeof(path))) {
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return 1;
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}
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auto* state = static_cast<TailState*>(calloc(1, sizeof(TailState)));
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if (state == nullptr) {
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printf("tail: out of memory\n");
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return 1;
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}
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if (!streamFile(path, state, collectTailChunk)) {
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printf("tail: %s: cannot read\n", argv[first]);
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free(state);
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return 1;
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}
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// A file not ending in a newline leaves a partial line in the buffer that still counts.
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if (state->columnn > 0) {
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state->lines[state->next][state->columnn] = '\0';
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state->next = (state->next + 1) % TAIL_MAX_LINES;
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if (state->count < TAIL_MAX_LINES) {
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state->count++;
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}
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}
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const int show = (count < state->count) ? count : state->count;
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for (int i = show; i > 0; i--) {
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const int index = (state->next - i + TAIL_MAX_LINES * 2) % TAIL_MAX_LINES;
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printf("%s\n", state->lines[index]);
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}
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free(state);
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return 0;
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}
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extern const ::AppManifest manifest = {
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.id = "tail",
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.name = "tail",
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.category = APP_CATEGORY_SYSTEM,
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.location = { .type = APP_LOCATION_MEMORY, .location = reinterpret_cast<void*>(main) },
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.flags = APP_MANIFEST_FLAG_HEADLESS,
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.stack = { .depth = 4096, .desired_memory_capability = 0 },
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};
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} // namespace coreutils::tail
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