util.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <utlist.h>
#include "mle.h"

static const unsigned char utf8_mask[6] = {0x7f, 0x1f, 0x0f, 0x07, 0x03, 0x01};

// Run a shell command, optionally feeding stdin, collecting stdout
// Specify timeout_s=-1 for no timeout
int util_shell_exec(editor_t *editor, char *cmd, long timeout_s, char *input, size_t input_len, int setsid, char *opt_shell, char **optret_output, size_t *optret_output_len, int *optret_exit_code) {
    // TODO clean this crap up
    int rv;
    int do_read;
    int do_write;
    int readfd;
    int writefd;
    ssize_t rc;
    ssize_t nbytes;
    fd_set readfds;
    struct timeval timeout;
    struct timeval *timeoutptr;
    pid_t pid;
    int exit_status;
    str_t readbuf = {0};

    do_read = optret_output != NULL ? 1 : 0;
    do_write = input && input_len > 0 ? 1 : 0;
    readfd = -1;
    writefd = -1;
    pid = -1;
    readbuf.inc = -2; // double capacity on each allocation
    rv = MLE_OK;
    nbytes = 0;
    if (do_read) {
        *optret_output = NULL;
        *optret_output_len = 0;
    }

    // Open cmd
    if (!util_popen2(
        cmd,
        setsid,
        opt_shell,
        do_read ? &readfd : NULL,
        do_write ? &writefd : NULL,
        &pid
    )) {
        MLE_RETURN_ERR(editor, "Failed to exec shell cmd: %s", cmd);
    }

    // Read-write loop
    do {
        // Write to shell cmd if input is remaining
        if (do_write && writefd >= 0) {
            rc = write(writefd, input, input_len);
            if (rc > 0) {
                input += rc;
                input_len -= rc;
                if (input_len < 1) {
                    close(writefd);
                    writefd = -1;
                }
            } else {
                // write err
                MLE_SET_ERR(editor, "write error: %s", strerror(errno));
                rv = MLE_ERR;
                break;
            }
        }

        // Read shell cmd, timing out after timeout_sec
        if (do_read) {
            if (timeout_s >= 0) {
                timeout.tv_sec = timeout_s;
                timeout.tv_usec = 0;
                timeoutptr = &timeout;
            } else {
                timeoutptr = NULL;
            }
            FD_ZERO(&readfds);
            FD_SET(readfd, &readfds);
            rc = select(readfd + 1, &readfds, NULL, NULL, timeoutptr);
            if (rc < 0) {
                // Err on select
                MLE_SET_ERR(editor, "select error: %s", strerror(errno));
                rv = MLE_ERR;
                break;
            } else if (rc == 0) {
                // Timed out
                rv = MLE_ERR;
                break;
            } else {
                // Read a kilobyte of data
                str_ensure_cap(&readbuf, readbuf.len + 1024);
                nbytes = read(readfd, readbuf.data + readbuf.len, 1024);
                if (nbytes < 0) {
                    // read err or EAGAIN/EWOULDBLOCK
                    MLE_SET_ERR(editor, "read error: %s", strerror(errno));
                    rv = MLE_ERR;
                    break;
                } else if (nbytes > 0) {
                    // Got data
                    readbuf.len += nbytes;
                }
            }
        }
    } while(nbytes > 0); // until EOF

    // Close pipes and reap child proc
    if (readfd >= 0) close(readfd);
    if (writefd >= 0) close(writefd);
    exit_status = -1;
    waitpid(pid, &exit_status, do_read ? WNOHANG : 0);
    if (optret_exit_code) *optret_exit_code = WEXITSTATUS(exit_status);

    if (do_read) {
        *optret_output = readbuf.data;
        *optret_output_len = readbuf.len;
    }

    // Force redraw to correct artifacts from child process writing to stderr.
    // Piping stderr to `/dev/null` in the child process would be cleaner,
    // however that breaks interactive apps like less(1) which require stdio
    // ttys to behave properly.
    if (!_editor.headless_mode) editor_force_redraw(&_editor);

    return rv;
}

// Like popen, but more control over pipes. Returns 1 on success, 0 on failure.
int util_popen2(char *cmd, int do_setsid, char *opt_shell, int *optret_fdread, int *optret_fdwrite, pid_t *optret_pid) {
    pid_t pid;
    int do_read;
    int do_write;
    int pout[2];
    int pin[2];

    // Set r/w
    do_read = optret_fdread != NULL ? 1 : 0;
    do_write = optret_fdwrite != NULL ? 1 : 0;

    // Set shell
    opt_shell = opt_shell ? opt_shell : "sh";

    // Make pipes
    if (do_read) if (pipe(pout)) return 0;
    if (do_write) if (pipe(pin)) return 0;

    // Fork
    pid = fork();
    if (pid < 0) {
        // Fork failed
        return 0;
    } else if (pid == 0) {
        // Child
        if (do_read) {
            close(pout[0]);
            dup2(pout[1], STDOUT_FILENO);
            close(pout[1]);
        }
        if (do_write) {
            close(pin[1]);
            dup2(pin[0], STDIN_FILENO);
            close(pin[0]);
        }
        if (do_setsid) setsid();
        execlp(opt_shell, opt_shell, "-c", cmd, NULL);
        exit(EXIT_FAILURE);
    }
    // Parent
    if (do_read) {
        close(pout[1]);
        *optret_fdread = pout[0];
    }
    if (do_write) {
        close(pin[0]);
        *optret_fdwrite = pin[1];
    }
    if (optret_pid) *optret_pid = pid;
    return 1;
}

// Return paired bracket if ch is a bracket, else return 0
int util_get_bracket_pair(uint32_t ch, int *optret_is_closing) {
    switch (ch) {
        case '[': if (optret_is_closing) *optret_is_closing = 0; return ']';
        case '(': if (optret_is_closing) *optret_is_closing = 0; return ')';
        case '{': if (optret_is_closing) *optret_is_closing = 0; return '}';
        case ']': if (optret_is_closing) *optret_is_closing = 1; return '[';
        case ')': if (optret_is_closing) *optret_is_closing = 1; return '(';
        case '}': if (optret_is_closing) *optret_is_closing = 1; return '{';
        default: return 0;
    }
    return 0;
}

// Return 1 if path is file
int util_is_file(char *path, char *opt_mode, FILE **optret_file) {
    struct stat sb;
    if (stat(path, &sb) != 0 || !S_ISREG(sb.st_mode)) return 0;
    if (opt_mode && optret_file) {
        *optret_file = fopen(path, opt_mode);
        if (!*optret_file) return 0;
    }
    return 1;
}

// Return 1 if path is dir
int util_is_dir(char *path) {
    struct stat sb;
    if (stat(path, &sb) != 0 || !S_ISDIR(sb.st_mode)) return 0;
    return 1;
}

// Return 1 if re matches subject
int util_pcre_match(char *re, char *subject, int subject_len, char **optret_capture, int *optret_capture_len) {
    int rc;
    pcre2_code *cre;
    int errcode;
    PCRE2_SIZE erroffset;
    PCRE2_SIZE ovector[3];
    cre = pcre2_compile((PCRE2_SPTR)re, (PCRE2_SIZE)strlen(re), (optret_capture ? 0 : PCRE2_NO_AUTO_CAPTURE) | PCRE2_CASELESS, &errcode, &erroffset, NULL);
    if (!cre) return 0;
    rc = pcre2_match(cre, (PCRE2_SPTR)subject, (PCRE2_SIZE)subject_len, 0, 0, pcre2_md, NULL);
    memcpy(ovector, pcre2_get_ovector_pointer(pcre2_md), 3 * sizeof(PCRE2_SIZE));
    pcre2_code_free(cre);
    if (optret_capture) {
        if (rc >= 0) {
            *optret_capture = subject + ovector[0];
            *optret_capture_len = ovector[1] - ovector[0];
        } else {
            *optret_capture = NULL;
            *optret_capture_len = 0;
        }
    }
    return rc >= 0 ? 1 : 0;
}

// Perform a regex replace with back-references. Return number of replacements
// made. If regex is invalid, `ret_result` is set to NULL, `ret_result_len` is
// set to 0 and 0 is returned.
int util_pcre_replace(char *re, char *subj, char *repl, char **ret_result, int *ret_result_len) {
    int rc;
    pcre2_code *cre;
    int errcode;
    PCRE2_SIZE erroffset;
    int subj_offset;
    int subj_offset_z;
    int subj_len;
    int subj_look_offset;
    int last_look_offset;
    PCRE2_SIZE ovector[30];
    int num_repls;
    int got_match = 0;
    str_t result = {0};

    *ret_result = NULL;
    *ret_result_len = 0;

    // Compile regex
    cre = pcre2_compile((PCRE2_SPTR)re, (PCRE2_SIZE)strlen(re), PCRE2_CASELESS, &errcode, &erroffset, NULL);
    if (!cre) return 0;

    // Start match-replace loop
    num_repls = 0;
    subj_len = strlen(subj);
    subj_offset = 0;
    subj_look_offset = 0;
    last_look_offset = 0;
    while (subj_offset < subj_len) {
        // Find match
        rc = pcre2_match(cre, (PCRE2_SPTR)subj, (PCRE2_SIZE)subj_len, (PCRE2_SIZE)subj_look_offset, 0, pcre2_md, NULL);
        memcpy(ovector, pcre2_get_ovector_pointer(pcre2_md), 30 * sizeof(PCRE2_SIZE));
        if (rc < 0 || ovector[0] == PCRE2_UNSET) {
            got_match = 0;
            subj_offset_z = subj_len;
        } else {
            got_match = 1;
            subj_offset_z = ovector[0];
        }

        // Append part before match
        str_append_stop(&result, subj + subj_offset, subj + subj_offset_z);
        subj_offset = ovector[1];
        subj_look_offset = subj_offset + (subj_offset > last_look_offset ? 0 : 1); // Prevent infinite loop
        last_look_offset = subj_look_offset;

        // Break if no match
        if (!got_match) break;

        // Append replacements with backrefs
        str_append_replace_with_backrefs(&result, subj, repl, rc, ovector, 30);

        // Increment num_repls
        num_repls += 1;
    }

    // Free regex
    pcre2_code_free(cre);

    // Return result
    *ret_result = result.data ? result.data : strdup("");
    *ret_result_len = result.len;

    // Return number of replacements
    return num_repls;
}

// Return 1 if a > b, else return 0.
int util_timeval_is_gt(struct timeval *a, struct timeval *b) {
    if (a->tv_sec > b->tv_sec) {
        return 1;
    } else if (a->tv_sec == b->tv_sec) {
        return a->tv_usec > b->tv_usec ? 1 : 0;
    }
    return 0;
}

// Ported from php_escape_shell_arg
// https://github.com/php/php-src/blob/master/ext/standard/exec.c
char *util_escape_shell_arg(char *str, int l) {
    int x, y = 0;
    char *cmd;

    cmd = malloc(4 * l + 3); // worst case

    cmd[y++] = '\'';

    for (x = 0; x < l; x++) {
        int mb_len = tb_utf8_char_length(*(str + x));

        // skip non-valid multibyte characters
        if (mb_len < 0) {
            continue;
        } else if (mb_len > 1) {
            memcpy(cmd + y, str + x, mb_len);
            y += mb_len;
            x += mb_len - 1;
            continue;
        }

        switch (str[x]) {
        case '\'':
            cmd[y++] = '\'';
            cmd[y++] = '\\';
            cmd[y++] = '\'';
            // fall-through
        default:
            cmd[y++] = str[x];
        }
    }
    cmd[y++] = '\'';
    cmd[y] = '\0';

    return cmd;
}

// Attempt to replace leading ~/ with $HOME
void util_expand_tilde(char *path, int path_len, char **ret_path, int *optret_path_len) {
    char *homedir;
    char *newpath;
    if (!util_is_file("~", NULL, NULL)
        && strncmp(path, "~/", 2) == 0
        && (homedir = getenv("HOME")) != NULL
    ) {
        newpath = malloc(strlen(homedir) + 1 + (path_len - 2) + 1);
        sprintf(newpath, "%s/%.*s", homedir, path_len-2, path+2);
        *ret_path = newpath;
        if (optret_path_len) *optret_path_len = strlen(*ret_path);
        return;
    }
    *ret_path = strndup(path, path_len);
    if (optret_path_len) *optret_path_len = strlen(*ret_path);
}

// Adapted from termbox src/demo/keyboard.c
int tb_printf_rect(bview_rect_t rect, int x, int y, uint16_t fg, uint16_t bg, const char *fmt, ...) {
    char buf[4096];
    va_list vl;
    va_start(vl, fmt);
    vsnprintf(buf, sizeof(buf), fmt, vl);
    va_end(vl);
    return tb_print(rect.x + x, rect.y + y, fg ? fg : rect.fg, bg ? bg : rect.bg, buf);
}

// Like tb_printf, but accepts @fg,bg; attributes inside the string. To print
// a literal '@', use '@@' in the format string. Specify fg or bg of 0 to
// reset that attribute.
int tb_printf_attr(bview_rect_t rect, int x, int y, const char *fmt, ...) {
    char bufo[4096];
    char *buf, *bufstop;
    int fg, bg, tfg, tbg, c, buflen;
    uint32_t uni;

    va_list vl;
    va_start(vl, fmt);
    buflen = vsnprintf(bufo, sizeof(bufo), fmt, vl);
    buflen = MLBUF_MIN(buflen, (int)(sizeof(bufo) - 1));
    va_end(vl);


    fg = rect.fg;
    bg = rect.bg;
    x = rect.x + x;
    y = rect.y + y;

    c = 0;
    buf = bufo;
    bufstop = buf + buflen;
    while (*buf) {
        buf += utf8_char_to_unicode(&uni, buf, bufstop);
        if (uni == '@') {
            if (!*buf) break;
            utf8_char_to_unicode(&uni, buf, bufstop);
            if (uni != '@') {
                tfg = strtol(buf, &buf, 10);
                if (!*buf) break;
                utf8_char_to_unicode(&uni, buf, bufstop);
                if (uni == ',') {
                    buf++;
                    if (!*buf) break;
                    tbg = strtol(buf, &buf, 10);
                    fg = tfg <= 0 ? rect.fg : tfg;
                    bg = tbg <= 0 ? rect.bg : tbg;
                    if (!*buf) break;
                    utf8_char_to_unicode(&uni, buf, bufstop);
                    if (uni == ';') buf++;
                    continue;
                }
            }
        }
        tb_set_cell(x, y, uni, fg, bg);
        x++;
        c++;
    }
    return c;
}


// Zero-fill realloc
void *recalloc(void *ptr, size_t orig_num, size_t new_num, size_t el_size) {
    void *newptr;
    newptr = realloc(ptr, new_num * el_size);
    if (!newptr) return NULL;
    if (new_num > orig_num) {
        memset(newptr + (orig_num * el_size), 0, (new_num - orig_num) * el_size);
    }
    return newptr;
}

// Append from data up until data_stop to str
void str_append_stop(str_t *str, char *data, char *data_stop) {
    size_t data_len;
    data_len = data_stop >= data ? data_stop - data : 0;
    str_append_len(str, data, data_len);
}

// Append data to str
void str_append(str_t *str, char *data) {
    str_append_len(str, data, strlen(data));
}

// Append data_len bytes of data to str
void str_append_len(str_t *str, char *data, size_t data_len) {
    str_put_len(str, data, data_len, 0);
}

// Append char to str
void str_append_char(str_t *str, char c) {
    str_put_len(str, &c, 1, 0);
}

// Prepend from data up until data_stop to str
void str_prepend_stop(str_t *str, char *data, char *data_stop) {
    size_t data_len;
    data_len = data_stop >= data ? data_stop - data : 0;
    str_prepend_len(str, data, data_len);
}

// Prepend data to str
void str_prepend(str_t *str, char *data) {
    str_prepend_len(str, data, strlen(data));
}

// Prepend data_len bytes of data to str
void str_prepend_len(str_t *str, char *data, size_t data_len) {
    str_put_len(str, data, data_len, 1);
}

// Set str to data
void str_set(str_t *str, char *data) {
    str_set_len(str, data, strlen(data));
}

// Set str to data for data_len bytes
void str_set_len(str_t *str, char *data, size_t data_len) {
    str_ensure_cap(str, data_len+1);
    memcpy(str->data, data, data_len);
    str->len = data_len;
    *(str->data + str->len) = '\0';
}

// Sprintf to str
void str_sprintf(str_t *str, const char *fmt, ...) {
    va_list va;
    int len;

    va_start(va, fmt);
    len = vsnprintf(NULL, 0, fmt, va);
    va_end(va);

    str_ensure_cap(str, str->len + (size_t)len + 1);

    va_start(va, fmt);
    vsprintf(str->data + str->len, fmt, va);
    va_end(va);

    str->len += (size_t)len;
}

// Append/prepend data_len bytes of data to str
void str_put_len(str_t *str, char *data, size_t data_len, int is_prepend) {
    size_t req_cap;
    req_cap = str->len + data_len + 1;

    str_ensure_cap(str, req_cap);

    if (is_prepend) {
        memmove(str->data + data_len, str->data, str->len);
        memcpy(str->data, data, data_len);
    } else {
        memcpy(str->data + str->len, data, data_len);
    }
    str->len += data_len;
    *(str->data + str->len) = '\0';
}

// Ensure space in str
void str_ensure_cap(str_t *str, size_t cap) {
    if (!str->data || cap > str->cap) {
        if (str->inc >= 0) {
            // If inc is positive, grow linearly
            cap = MLBUF_MAX(cap, str->cap + (str->inc > 0 ? str->inc : 128));
        } else {
            // If inc is negative, grow geometrically
            cap = MLBUF_MAX(cap, str->cap * (str->inc <= -2 ? str->inc * -1 : 2));
        }
        str->data = realloc(str->data, cap);
        str->cap = cap;
    }
}

// Clear str
void str_clear(str_t *str) {
    str->len = 0;
}

// Free str
void str_free(str_t *str) {
    if (str->data) free(str->data);
    memset(str, 0, sizeof(str_t));
}

// Replace `repl` in `subj` and append result to `str`. PCRE style backrefs are
// supported.
//
//   str           where to append data
//   subj          subject string
//   repl          replacement string with $1 or \1 style backrefs
//   pcre_rc       return code from pcre_exec
//   pcre_ovector  ovector used with pcre_exec
//   pcre_ovecsize size of pcre_ovector
//
void str_append_replace_with_backrefs(str_t *str, char *subj, char *repl, int pcre_rc, PCRE2_SIZE *pcre_ovector, int pcre_ovecsize) {
    char *repl_stop;
    char *repl_cur;
    char *repl_z;
    char *repl_backref;
    int repl_delta;
    int ibackref;
    char *term;
    char *term_stop;
    char hex[3];
    char byte;

    repl_stop = repl + strlen(repl);

    // Start replace loop
    repl_cur = repl;
    while (repl_cur < repl_stop) {
        // Find backref marker (dollar sign or backslash) in replacement str
        repl_backref = strpbrk(repl_cur, "$\\");
        repl_z = repl_backref ? repl_backref : repl_stop;

        // Append part before backref
        str_append_stop(str, repl_cur, repl_z);

        // Break if no backref
        if (!repl_backref) break;

        // Append backref
        term = NULL;
        repl_delta = 2; // marker + backref symbol
        if (repl_backref+1 >= repl_stop) {
            // No data after backref marker; append the marker itself
            term = repl_backref;
            term_stop = repl_stop;
        } else if (*(repl_backref+1) >= '0' && *(repl_backref+1) <= '9') {
            // $N; append Nth captured substring from match
            ibackref = *(repl_backref+1) - '0';
            if (ibackref < pcre_rc && ibackref < pcre_ovecsize/3) {
                // Backref exists
                term = subj + pcre_ovector[ibackref*2];
                term_stop = subj + pcre_ovector[ibackref*2 + 1];
            } else {
                // Backref does not exist; append marker + whatever character it was
                term = repl_backref;
                term_stop = term + tb_utf8_char_length(*(term+1));
            }
        } else if (*(repl_backref+1) == 'n') {
            // $n; append newline
            term = "\n";
            term_stop = term + 1;
        } else if (*(repl_backref+1) == 't') {
            // $t; append tab
            term = "\t";
            term_stop = term + 1;
        } else if (*(repl_backref+1) == 'x' && repl_backref+3 < repl_stop) {
            // $xNN; append byte
            strncpy(hex, repl_backref+2, 2);
            hex[2] = '\0';
            byte = strtoul(hex, NULL, 16);
            term = &byte;
            term_stop = term + 1;
            repl_delta = 4; // marker + 'x' + d1 + d2
        } else {
            // $* (not number or 'n'); append marker + whatever character it was
            term = repl_backref;
            term_stop = term + tb_utf8_char_length(*(term+1));
        }
        str_append_stop(str, term, term_stop);

        // Advance repl_cur by repl_delta bytes
        repl_cur = repl_backref + repl_delta;
    }
}

// Return a new aproc_t
aproc_t *aproc_new(editor_t *editor, void *owner, aproc_t **owner_aproc, char *shell_cmd, int rw, aproc_cb_t callback) {
    aproc_t *aproc;
    aproc = calloc(1, sizeof(aproc_t));
    aproc->editor = editor;
    aproc_set_owner(aproc, owner, owner_aproc);
    if (rw) {
        if (!util_popen2(shell_cmd, 0, NULL, &aproc->rfd, &aproc->wfd, &aproc->pid)) {
            goto aproc_new_failure;
        }
        aproc->rpipe = fdopen(aproc->rfd, "r");
        aproc->wpipe = fdopen(aproc->wfd, "w");
    } else {
        if (!(aproc->rpipe = popen(shell_cmd, "r"))) {
            goto aproc_new_failure;
        }
        aproc->rfd = fileno(aproc->rpipe);
    }
    setvbuf(aproc->rpipe, NULL, _IONBF, 0);
    if (aproc->wpipe) setvbuf(aproc->wpipe, NULL, _IONBF, 0);
    aproc->callback = callback;
    DL_APPEND(editor->aprocs, aproc);
    return aproc;

aproc_new_failure:
    free(aproc);
    return NULL;
}

// Set aproc owner
int aproc_set_owner(aproc_t *aproc, void *owner, aproc_t **owner_aproc) {
    if (aproc->owner_aproc) {
        *aproc->owner_aproc = NULL;
    }
    *owner_aproc = aproc;
    aproc->owner = owner;
    aproc->owner_aproc = owner_aproc;
    return MLE_OK;
}

// Destroy an aproc_t
int aproc_destroy(aproc_t *aproc, int preempt) {
    DL_DELETE(aproc->editor->aprocs, aproc);
    if (aproc->owner_aproc) *aproc->owner_aproc = NULL;
    if (preempt) {
        if (aproc->rfd) close(aproc->rfd);
        if (aproc->wfd) close(aproc->wfd);
        if (aproc->pid) kill(aproc->pid, SIGTERM);
    }
    if (aproc->rpipe) pclose(aproc->rpipe);
    if (aproc->wpipe) pclose(aproc->wpipe);
    free(aproc);
    return MLE_OK;
}

// Manage async procs, giving priority to user input. Return 1 if drain should
// be called again, else return 0.
int aproc_drain_all(aproc_t *aprocs, int *ttyfd) {
    int maxfd;
    fd_set readfds;
    aproc_t *aproc;
    aproc_t *aproc_tmp;
    char buf[1024 + 1];
    ssize_t nbytes;
    int rc;

    // Exit early if no aprocs
    if (!aprocs) return 0;

    // Open ttyfd if not already open
    if (!*ttyfd) {
        if ((*ttyfd = open("/dev/tty", O_RDONLY)) < 0) {
            // TODO error
            return 0;
        }
    }

    // Add tty to readfds
    FD_ZERO(&readfds);
    FD_SET(*ttyfd, &readfds);

    // Add async procs to readfds
    // Simultaneously check for solo, which takes precedence over everything
    maxfd = *ttyfd;
    DL_FOREACH(aprocs, aproc) {
        FD_SET(aproc->rfd, &readfds);
        if (aproc->rfd > maxfd) maxfd = aproc->rfd;
    }

    // Perform select
    rc = select(maxfd + 1, &readfds, NULL, NULL, NULL);
    if (rc < 0) {
        return 0; // TODO error
    } else if (rc == 0) {
        return 1; // Nothing to read, call again
    }

    if (FD_ISSET(*ttyfd, &readfds)) {
        // Immediately give priority to user input
        return 0;
    } else {
        // Read async procs
        DL_FOREACH_SAFE(aprocs, aproc, aproc_tmp) {
            // Read and invoke callback
            if (FD_ISSET(aproc->rfd, &readfds)) {
                nbytes = read(aproc->rfd, &buf, 1024);
                buf[nbytes] = '\0';
                aproc->callback(aproc, buf, nbytes);
                if (nbytes == 0) aproc->is_done = 1;
            }
            // Destroy on eof.
            // Not sure if ferror and feof have any effect here given we're not
            // using fread.
            if (ferror(aproc->rpipe) || feof(aproc->rpipe) || aproc->is_done) {
                aproc_destroy(aproc, 0);
            }
        }
    }

    return 1;
}

size_t utf8_str_length(char *data, size_t len) {
    size_t slen;
    char *data_stop, *c;
    data_stop = data + len;
    c = data;
    slen = 0;
    while (c < data_stop) {
        c += tb_utf8_char_length(*c);
        slen += 1;
    }
    return slen;
}

// Like tb_utf8_char_to_unicode but obeys `stop` and returns U+FFFD if invalid
int utf8_char_to_unicode(uint32_t *out, const char *c, const char *stop) {
    if (*c == '\0') return 0;

    int i;
    unsigned char len = tb_utf8_char_length(*c);
    unsigned char mask = utf8_mask[len - 1];
    uint32_t result = c[0] & mask;
    for (i = 1; i < len && (c + i) < stop; ++i) {
        result <<= 6;
        result |= c[i] & 0x3f;
    }

    if (i != len) {
        result = 0xfffd; // replace incomplete code point with replacement char
        len = i;
    }

    *out = result;
    return (int)len;
}