bytesobject.c

/* bytes object implementation */

#define PY_SSIZE_T_CLEAN

#include "Python.h"

#include "bytes_methods.h"
#include "pystrhex.h"
#include <stddef.h>

/*[clinic input]
class bytes "PyBytesObject*" "&PyBytes_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=1a1d9102afc1b00c]*/

#include "clinic/bytesobject.c.h"

#ifdef COUNT_ALLOCS
Py_ssize_t null_strings, one_strings;
#endif

static PyBytesObject *characters[UCHAR_MAX + 1];
static PyBytesObject *nullstring;

/* PyBytesObject_SIZE gives the basic size of a string; any memory allocation
   for a string of length n should request PyBytesObject_SIZE + n bytes.

   Using PyBytesObject_SIZE instead of sizeof(PyBytesObject) saves
   3 bytes per string allocation on a typical system.
*/
#define PyBytesObject_SIZE (offsetof(PyBytesObject, ob_sval) + 1)

/* Forward declaration */
Py_LOCAL_INLINE(Py_ssize_t) _PyBytesWriter_GetSize(_PyBytesWriter *writer,
                                                   char *str);

/*
   For PyBytes_FromString(), the parameter `str' points to a null-terminated
   string containing exactly `size' bytes.

   For PyBytes_FromStringAndSize(), the parameter the parameter `str' is
   either NULL or else points to a string containing at least `size' bytes.
   For PyBytes_FromStringAndSize(), the string in the `str' parameter does
   not have to be null-terminated.  (Therefore it is safe to construct a
   substring by calling `PyBytes_FromStringAndSize(origstring, substrlen)'.)
   If `str' is NULL then PyBytes_FromStringAndSize() will allocate `size+1'
   bytes (setting the last byte to the null terminating character) and you can
   fill in the data yourself.  If `str' is non-NULL then the resulting
   PyBytes object must be treated as immutable and you must not fill in nor
   alter the data yourself, since the strings may be shared.

   The PyObject member `op->ob_size', which denotes the number of "extra
   items" in a variable-size object, will contain the number of bytes
   allocated for string data, not counting the null terminating character.
   It is therefore equal to the `size' parameter (for
   PyBytes_FromStringAndSize()) or the length of the string in the `str'
   parameter (for PyBytes_FromString()).
*/
static PyObject *
_PyBytes_FromSize(Py_ssize_t size, int use_calloc)
{
    PyBytesObject *op;
    assert(size >= 0);

    if (size == 0 && (op = nullstring) != NULL) {
#ifdef COUNT_ALLOCS
        null_strings++;
#endif
        Py_INCREF(op);
        return (PyObject *)op;
    }

    if ((size_t)size > (size_t)PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
        PyErr_SetString(PyExc_OverflowError,
                        "byte string is too large");
        return NULL;
    }

    /* Inline PyObject_NewVar */
    if (use_calloc)
        op = (PyBytesObject *)PyObject_Calloc(1, PyBytesObject_SIZE + size);
    else
        op = (PyBytesObject *)PyObject_Malloc(PyBytesObject_SIZE + size);
    if (op == NULL)
        return PyErr_NoMemory();
    (void)PyObject_INIT_VAR(op, &PyBytes_Type, size);
    op->ob_shash = -1;
    if (!use_calloc)
        op->ob_sval[size] = '\0';
    /* empty byte string singleton */
    if (size == 0) {
        nullstring = op;
        Py_INCREF(op);
    }
    return (PyObject *) op;
}

PyObject *
PyBytes_FromStringAndSize(const char *str, Py_ssize_t size)
{
    PyBytesObject *op;
    if (size < 0) {
        PyErr_SetString(PyExc_SystemError,
            "Negative size passed to PyBytes_FromStringAndSize");
        return NULL;
    }
    if (size == 1 && str != NULL &&
        (op = characters[*str & UCHAR_MAX]) != NULL)
    {
#ifdef COUNT_ALLOCS
        one_strings++;
#endif
        Py_INCREF(op);
        return (PyObject *)op;
    }

    op = (PyBytesObject *)_PyBytes_FromSize(size, 0);
    if (op == NULL)
        return NULL;
    if (str == NULL)
        return (PyObject *) op;

    Py_MEMCPY(op->ob_sval, str, size);
    /* share short strings */
    if (size == 1) {
        characters[*str & UCHAR_MAX] = op;
        Py_INCREF(op);
    }
    return (PyObject *) op;
}

PyObject *
PyBytes_FromString(const char *str)
{
    size_t size;
    PyBytesObject *op;

    assert(str != NULL);
    size = strlen(str);
    if (size > PY_SSIZE_T_MAX - PyBytesObject_SIZE) {
        PyErr_SetString(PyExc_OverflowError,
            "byte string is too long");
        return NULL;
    }
    if (size == 0 && (op = nullstring) != NULL) {
#ifdef COUNT_ALLOCS
        null_strings++;
#endif
        Py_INCREF(op);
        return (PyObject *)op;
    }
    if (size == 1 && (op = characters[*str & UCHAR_MAX]) != NULL) {
#ifdef COUNT_ALLOCS
        one_strings++;
#endif
        Py_INCREF(op);
        return (PyObject *)op;
    }

    /* Inline PyObject_NewVar */
    op = (PyBytesObject *)PyObject_MALLOC(PyBytesObject_SIZE + size);
    if (op == NULL)
        return PyErr_NoMemory();
    (void)PyObject_INIT_VAR(op, &PyBytes_Type, size);
    op->ob_shash = -1;
    Py_MEMCPY(op->ob_sval, str, size+1);
    /* share short strings */
    if (size == 0) {
        nullstring = op;
        Py_INCREF(op);
    } else if (size == 1) {
        characters[*str & UCHAR_MAX] = op;
        Py_INCREF(op);
    }
    return (PyObject *) op;
}

PyObject *
PyBytes_FromFormatV(const char *format, va_list vargs)
{
    char *s;
    const char *f;
    const char *p;
    Py_ssize_t prec;
    int longflag;
    int size_tflag;
    /* Longest 64-bit formatted numbers:
       - "18446744073709551615\0" (21 bytes)
       - "-9223372036854775808\0" (21 bytes)
       Decimal takes the most space (it isn't enough for octal.)

       Longest 64-bit pointer representation:
       "0xffffffffffffffff\0" (19 bytes). */
    char buffer[21];
    _PyBytesWriter writer;

    _PyBytesWriter_Init(&writer);

    s = _PyBytesWriter_Alloc(&writer, strlen(format));
    if (s == NULL)
        return NULL;
    writer.overallocate = 1;

#define WRITE_BYTES(str) \
    do { \
        s = _PyBytesWriter_WriteBytes(&writer, s, (str), strlen(str)); \
        if (s == NULL) \
            goto error; \
    } while (0)

    for (f = format; *f; f++) {
        if (*f != '%') {
            *s++ = *f;
            continue;
        }

        p = f++;

        /* ignore the width (ex: 10 in "%10s") */
        while (Py_ISDIGIT(*f))
            f++;

        /* parse the precision (ex: 10 in "%.10s") */
        prec = 0;
        if (*f == '.') {
            f++;
            for (; Py_ISDIGIT(*f); f++) {
                prec = (prec * 10) + (*f - '0');
            }
        }

        while (*f && *f != '%' && !Py_ISALPHA(*f))
            f++;

        /* handle the long flag ('l'), but only for %ld and %lu.
           others can be added when necessary. */
        longflag = 0;
        if (*f == 'l' && (f[1] == 'd' || f[1] == 'u')) {
            longflag = 1;
            ++f;
        }

        /* handle the size_t flag ('z'). */
        size_tflag = 0;
        if (*f == 'z' && (f[1] == 'd' || f[1] == 'u')) {
            size_tflag = 1;
            ++f;
        }

        /* substract bytes preallocated for the format string
           (ex: 2 for "%s") */
        writer.min_size -= (f - p + 1);

        switch (*f) {
        case 'c':
        {
            int c = va_arg(vargs, int);
            if (c < 0 || c > 255) {
                PyErr_SetString(PyExc_OverflowError,
                                "PyBytes_FromFormatV(): %c format "
                                "expects an integer in range [0; 255]");
                goto error;
            }
            writer.min_size++;
            *s++ = (unsigned char)c;
            break;
        }

        case 'd':
            if (longflag)
                sprintf(buffer, "%ld", va_arg(vargs, long));
            else if (size_tflag)
                sprintf(buffer, "%" PY_FORMAT_SIZE_T "d",
                    va_arg(vargs, Py_ssize_t));
            else
                sprintf(buffer, "%d", va_arg(vargs, int));
            assert(strlen(buffer) < sizeof(buffer));
            WRITE_BYTES(buffer);
            break;

        case 'u':
            if (longflag)
                sprintf(buffer, "%lu",
                    va_arg(vargs, unsigned long));
            else if (size_tflag)
                sprintf(buffer, "%" PY_FORMAT_SIZE_T "u",
                    va_arg(vargs, size_t));
            else
                sprintf(buffer, "%u",
                    va_arg(vargs, unsigned int));
            assert(strlen(buffer) < sizeof(buffer));
            WRITE_BYTES(buffer);
            break;

        case 'i':
            sprintf(buffer, "%i", va_arg(vargs, int));
            assert(strlen(buffer) < sizeof(buffer));
            WRITE_BYTES(buffer);
            break;

        case 'x':
            sprintf(buffer, "%x", va_arg(vargs, int));
            assert(strlen(buffer) < sizeof(buffer));
            WRITE_BYTES(buffer);
            break;

        case 's':
        {
            Py_ssize_t i;

            p = va_arg(vargs, const char*);
            i = strlen(p);
            if (prec > 0 && i > prec)
                i = prec;
            s = _PyBytesWriter_WriteBytes(&writer, s, p, i);
            if (s == NULL)
                goto error;
            break;
        }

        case 'p':
            sprintf(buffer, "%p", va_arg(vargs, void*));
            assert(strlen(buffer) < sizeof(buffer));
            /* %p is ill-defined:  ensure leading 0x. */
            if (buffer[1] == 'X')
                buffer[1] = 'x';
            else if (buffer[1] != 'x') {
                memmove(buffer+2, buffer, strlen(buffer)+1);
                buffer[0] = '0';
                buffer[1] = 'x';
            }
            WRITE_BYTES(buffer);
            break;

        case '%':
            writer.min_size++;
            *s++ = '%';
            break;

        default:
            if (*f == 0) {
                /* fix min_size if we reached the end of the format string */
                writer.min_size++;
            }

            /* invalid format string: copy unformatted string and exit */
            WRITE_BYTES(p);
            return _PyBytesWriter_Finish(&writer, s);
        }
    }

#undef WRITE_BYTES

    return _PyBytesWriter_Finish(&writer, s);

 error:
    _PyBytesWriter_Dealloc(&writer);
    return NULL;
}

PyObject *
PyBytes_FromFormat(const char *format, ...)
{
    PyObject* ret;
    va_list vargs;

#ifdef HAVE_STDARG_PROTOTYPES
    va_start(vargs, format);
#else
    va_start(vargs);
#endif
    ret = PyBytes_FromFormatV(format, vargs);
    va_end(vargs);
    return ret;
}

/* Helpers for formatstring */

Py_LOCAL_INLINE(PyObject *)
getnextarg(PyObject *args, Py_ssize_t arglen, Py_ssize_t *p_argidx)
{
    Py_ssize_t argidx = *p_argidx;
    if (argidx < arglen) {
        (*p_argidx)++;
        if (arglen < 0)
            return args;
        else
            return PyTuple_GetItem(args, argidx);
    }
    PyErr_SetString(PyExc_TypeError,
                    "not enough arguments for format string");
    return NULL;
}

/* Format codes
 * F_LJUST      '-'
 * F_SIGN       '+'
 * F_BLANK      ' '
 * F_ALT        '#'
 * F_ZERO       '0'
 */
#define F_LJUST (1<<0)
#define F_SIGN  (1<<1)
#define F_BLANK (1<<2)
#define F_ALT   (1<<3)
#define F_ZERO  (1<<4)

/* Returns a new reference to a PyBytes object, or NULL on failure. */

static char*
formatfloat(PyObject *v, int flags, int prec, int type,
            PyObject **p_result, _PyBytesWriter *writer, char *str)
{
    char *p;
    PyObject *result;
    double x;
    size_t len;

    x = PyFloat_AsDouble(v);
    if (x == -1.0 && PyErr_Occurred()) {
        PyErr_Format(PyExc_TypeError, "float argument required, "
                     "not %.200s", Py_TYPE(v)->tp_name);
        return NULL;
    }

    if (prec < 0)
        prec = 6;

    p = PyOS_double_to_string(x, type, prec,
                              (flags & F_ALT) ? Py_DTSF_ALT : 0, NULL);

    if (p == NULL)
        return NULL;

    len = strlen(p);
    if (writer != NULL) {
        str = _PyBytesWriter_Prepare(writer, str, len);
        if (str == NULL)
            return NULL;
        Py_MEMCPY(str, p, len);
        PyMem_Free(p);
        str += len;
        return str;
    }

    result = PyBytes_FromStringAndSize(p, len);
    PyMem_Free(p);
    *p_result = result;
    return str;
}

static PyObject *
formatlong(PyObject *v, int flags, int prec, int type)
{
    PyObject *result, *iobj;
    if (type == 'i')
        type = 'd';
    if (PyLong_Check(v))
        return _PyUnicode_FormatLong(v, flags & F_ALT, prec, type);
    if (PyNumber_Check(v)) {
        /* make sure number is a type of integer for o, x, and X */
        if (type == 'o' || type == 'x' || type == 'X')
            iobj = PyNumber_Index(v);
        else
            iobj = PyNumber_Long(v);
        if (iobj == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_TypeError))
                return NULL;
        }
        else if (!PyLong_Check(iobj))
            Py_CLEAR(iobj);
        if (iobj != NULL) {
            result = _PyUnicode_FormatLong(iobj, flags & F_ALT, prec, type);
            Py_DECREF(iobj);
            return result;
        }
    }
    PyErr_Format(PyExc_TypeError,
        "%%%c format: %s is required, not %.200s", type,
        (type == 'o' || type == 'x' || type == 'X') ? "an integer"
                                                    : "a number",
        Py_TYPE(v)->tp_name);
    return NULL;
}

static int
byte_converter(PyObject *arg, char *p)
{
    if (PyBytes_Check(arg) && PyBytes_Size(arg) == 1) {
        *p = PyBytes_AS_STRING(arg)[0];
        return 1;
    }
    else if (PyByteArray_Check(arg) && PyByteArray_Size(arg) == 1) {
        *p = PyByteArray_AS_STRING(arg)[0];
        return 1;
    }
    else {
        PyObject *iobj;
        long ival;
        int overflow;
        /* make sure number is a type of integer */
        if (PyLong_Check(arg)) {
            ival = PyLong_AsLongAndOverflow(arg, &overflow);
        }
        else {
            iobj = PyNumber_Index(arg);
            if (iobj == NULL) {
                if (!PyErr_ExceptionMatches(PyExc_TypeError))
                    return 0;
                goto onError;
            }
            ival = PyLong_AsLongAndOverflow(iobj, &overflow);
            Py_DECREF(iobj);
        }
        if (!overflow && ival == -1 && PyErr_Occurred())
            goto onError;
        if (overflow || !(0 <= ival && ival <= 255)) {
            PyErr_SetString(PyExc_OverflowError,
                            "%c arg not in range(256)");
            return 0;
        }
        *p = (char)ival;
        return 1;
    }
  onError:
    PyErr_SetString(PyExc_TypeError,
        "%c requires an integer in range(256) or a single byte");
    return 0;
}

static PyObject *
format_obj(PyObject *v, const char **pbuf, Py_ssize_t *plen)
{
    PyObject *func, *result;
    _Py_IDENTIFIER(__bytes__);
    /* is it a bytes object? */
    if (PyBytes_Check(v)) {
        *pbuf = PyBytes_AS_STRING(v);
        *plen = PyBytes_GET_SIZE(v);
        Py_INCREF(v);
        return v;
    }
    if (PyByteArray_Check(v)) {
        *pbuf = PyByteArray_AS_STRING(v);
        *plen = PyByteArray_GET_SIZE(v);
        Py_INCREF(v);
        return v;
    }
    /* does it support __bytes__? */
    func = _PyObject_LookupSpecial(v, &PyId___bytes__);
    if (func != NULL) {
        result = PyObject_CallFunctionObjArgs(func, NULL);
        Py_DECREF(func);
        if (result == NULL)
            return NULL;
        if (!PyBytes_Check(result)) {
            PyErr_Format(PyExc_TypeError,
                         "__bytes__ returned non-bytes (type %.200s)",
                         Py_TYPE(result)->tp_name);
            Py_DECREF(result);
            return NULL;
        }
        *pbuf = PyBytes_AS_STRING(result);
        *plen = PyBytes_GET_SIZE(result);
        return result;
    }
    PyErr_Format(PyExc_TypeError,
                 "%%b requires bytes, or an object that implements __bytes__, not '%.100s'",
                 Py_TYPE(v)->tp_name);
    return NULL;
}

/* fmt%(v1,v2,...) is roughly equivalent to sprintf(fmt, v1, v2, ...) */

PyObject *
_PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
                  PyObject *args, int use_bytearray)
{
    const char *fmt;
    char *res;
    Py_ssize_t arglen, argidx;
    Py_ssize_t fmtcnt;
    int args_owned = 0;
    PyObject *dict = NULL;
    _PyBytesWriter writer;

    if (args == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }
    fmt = format;
    fmtcnt = format_len;

    _PyBytesWriter_Init(&writer);
    writer.use_bytearray = use_bytearray;

    res = _PyBytesWriter_Alloc(&writer, fmtcnt);
    if (res == NULL)
        return NULL;
    if (!use_bytearray)
        writer.overallocate = 1;

    if (PyTuple_Check(args)) {
        arglen = PyTuple_GET_SIZE(args);
        argidx = 0;
    }
    else {
        arglen = -1;
        argidx = -2;
    }
    if (Py_TYPE(args)->tp_as_mapping && Py_TYPE(args)->tp_as_mapping->mp_subscript &&
        !PyTuple_Check(args) && !PyBytes_Check(args) && !PyUnicode_Check(args) &&
        !PyByteArray_Check(args)) {
            dict = args;
    }

    while (--fmtcnt >= 0) {
        if (*fmt != '%') {
            Py_ssize_t len;
            char *pos;

            pos = strchr(fmt + 1, '%');
            if (pos != NULL)
                len = pos - fmt;
            else
                len = format_len - (fmt - format);
            assert(len != 0);

            Py_MEMCPY(res, fmt, len);
            res += len;
            fmt += len;
            fmtcnt -= (len - 1);
        }
        else {
            /* Got a format specifier */
            int flags = 0;
            Py_ssize_t width = -1;
            int prec = -1;
            int c = '\0';
            int fill;
            PyObject *v = NULL;
            PyObject *temp = NULL;
            const char *pbuf = NULL;
            int sign;
            Py_ssize_t len = 0;
            char onechar; /* For byte_converter() */
            Py_ssize_t alloc;
#ifdef Py_DEBUG
            char *before;
#endif

            fmt++;
            if (*fmt == '(') {
                const char *keystart;
                Py_ssize_t keylen;
                PyObject *key;
                int pcount = 1;

                if (dict == NULL) {
                    PyErr_SetString(PyExc_TypeError,
                             "format requires a mapping");
                    goto error;
                }
                ++fmt;
                --fmtcnt;
                keystart = fmt;
                /* Skip over balanced parentheses */
                while (pcount > 0 && --fmtcnt >= 0) {
                    if (*fmt == ')')
                        --pcount;
                    else if (*fmt == '(')
                        ++pcount;
                    fmt++;
                }
                keylen = fmt - keystart - 1;
                if (fmtcnt < 0 || pcount > 0) {
                    PyErr_SetString(PyExc_ValueError,
                               "incomplete format key");
                    goto error;
                }
                key = PyBytes_FromStringAndSize(keystart,
                                                 keylen);
                if (key == NULL)
                    goto error;
                if (args_owned) {
                    Py_DECREF(args);
                    args_owned = 0;
                }
                args = PyObject_GetItem(dict, key);
                Py_DECREF(key);
                if (args == NULL) {
                    goto error;
                }
                args_owned = 1;
                arglen = -1;
                argidx = -2;
            }

            /* Parse flags. Example: "%+i" => flags=F_SIGN. */
            while (--fmtcnt >= 0) {
                switch (c = *fmt++) {
                case '-': flags |= F_LJUST; continue;
                case '+': flags |= F_SIGN; continue;
                case ' ': flags |= F_BLANK; continue;
                case '#': flags |= F_ALT; continue;
                case '0': flags |= F_ZERO; continue;
                }
                break;
            }

            /* Parse width. Example: "%10s" => width=10 */
            if (c == '*') {
                v = getnextarg(args, arglen, &argidx);
                if (v == NULL)
                    goto error;
                if (!PyLong_Check(v)) {
                    PyErr_SetString(PyExc_TypeError,
                                    "* wants int");
                    goto error;
                }
                width = PyLong_AsSsize_t(v);
                if (width == -1 && PyErr_Occurred())
                    goto error;
                if (width < 0) {
                    flags |= F_LJUST;
                    width = -width;
                }
                if (--fmtcnt >= 0)
                    c = *fmt++;
            }
            else if (c >= 0 && isdigit(c)) {
                width = c - '0';
                while (--fmtcnt >= 0) {
                    c = Py_CHARMASK(*fmt++);
                    if (!isdigit(c))
                        break;
                    if (width > (PY_SSIZE_T_MAX - ((int)c - '0')) / 10) {
                        PyErr_SetString(
                            PyExc_ValueError,
                            "width too big");
                        goto error;
                    }
                    width = width*10 + (c - '0');
                }
            }

            /* Parse precision. Example: "%.3f" => prec=3 */
            if (c == '.') {
                prec = 0;
                if (--fmtcnt >= 0)
                    c = *fmt++;
                if (c == '*') {
                    v = getnextarg(args, arglen, &argidx);
                    if (v == NULL)
                        goto error;
                    if (!PyLong_Check(v)) {
                        PyErr_SetString(
                            PyExc_TypeError,
                            "* wants int");
                        goto error;
                    }
                    prec = _PyLong_AsInt(v);
                    if (prec == -1 && PyErr_Occurred())
                        goto error;
                    if (prec < 0)
                        prec = 0;
                    if (--fmtcnt >= 0)
                        c = *fmt++;
                }
                else if (c >= 0 && isdigit(c)) {
                    prec = c - '0';
                    while (--fmtcnt >= 0) {
                        c = Py_CHARMASK(*fmt++);
                        if (!isdigit(c))
                            break;
                        if (prec > (INT_MAX - ((int)c - '0')) / 10) {
                            PyErr_SetString(
                                PyExc_ValueError,
                                "prec too big");
                            goto error;
                        }
                        prec = prec*10 + (c - '0');
                    }
                }
            } /* prec */
            if (fmtcnt >= 0) {
                if (c == 'h' || c == 'l' || c == 'L') {
                    if (--fmtcnt >= 0)
                        c = *fmt++;
                }
            }
            if (fmtcnt < 0) {
                PyErr_SetString(PyExc_ValueError,
                                "incomplete format");
                goto error;
            }
            if (c != '%') {
                v = getnextarg(args, arglen, &argidx);
                if (v == NULL)
                    goto error;
            }

            if (fmtcnt < 0) {
                /* last writer: disable writer overallocation */
                writer.overallocate = 0;
            }

            sign = 0;
            fill = ' ';
            switch (c) {
            case '%':
                *res++ = '%';
                continue;

            case 'r':
                // %r is only for 2/3 code; 3 only code should use %a
            case 'a':
                temp = PyObject_ASCII(v);
                if (temp == NULL)
                    goto error;
                assert(PyUnicode_IS_ASCII(temp));
                pbuf = (const char *)PyUnicode_1BYTE_DATA(temp);
                len = PyUnicode_GET_LENGTH(temp);
                if (prec >= 0 && len > prec)
                    len = prec;
                break;

            case 's':
                // %s is only for 2/3 code; 3 only code should use %b
            case 'b':
                temp = format_obj(v, &pbuf, &len);
                if (temp == NULL)
                    goto error;
                if (prec >= 0 && len > prec)
                    len = prec;
                break;

            case 'i':
            case 'd':
            case 'u':
            case 'o':
            case 'x':
            case 'X':
                if (PyLong_CheckExact(v)
                    && width == -1 && prec == -1
                    && !(flags & (F_SIGN | F_BLANK))
                    && c != 'X')
                {
                    /* Fast path */
                    int alternate = flags & F_ALT;
                    int base;

                    switch(c)
                    {
                        default:
                            assert(0 && "'type' not in [diuoxX]");
                        case 'd':
                        case 'i':
                        case 'u':
                            base = 10;
                            break;
                        case 'o':
                            base = 8;
                            break;
                        case 'x':
                        case 'X':
                            base = 16;
                            break;
                    }

                    /* Fast path */
                    writer.min_size -= 2; /* size preallocated for "%d" */
                    res = _PyLong_FormatBytesWriter(&writer, res,
                                                    v, base, alternate);
                    if (res == NULL)
                        goto error;
                    continue;
                }

                temp = formatlong(v, flags, prec, c);
                if (!temp)
                    goto error;
                assert(PyUnicode_IS_ASCII(temp));
                pbuf = (const char *)PyUnicode_1BYTE_DATA(temp);
                len = PyUnicode_GET_LENGTH(temp);
                sign = 1;
                if (flags & F_ZERO)
                    fill = '0';
                break;

            case 'e':
            case 'E':
            case 'f':
            case 'F':
            case 'g':
            case 'G':
                if (width == -1 && prec == -1
                    && !(flags & (F_SIGN | F_BLANK)))
                {
                    /* Fast path */
                    writer.min_size -= 2; /* size preallocated for "%f" */
                    res = formatfloat(v, flags, prec, c, NULL, &writer, res);
                    if (res == NULL)
                        goto error;
                    continue;
                }

                if (!formatfloat(v, flags, prec, c, &temp, NULL, res))
                    goto error;
                pbuf = PyBytes_AS_STRING(temp);
                len = PyBytes_GET_SIZE(temp);
                sign = 1;
                if (flags & F_ZERO)
                    fill = '0';
                break;

            case 'c':
                pbuf = &onechar;
                len = byte_converter(v, &onechar);
                if (!len)
                    goto error;
                if (width == -1) {
                    /* Fast path */
                    *res++ = onechar;
                    continue;
                }
                break;

            default:
                PyErr_Format(PyExc_ValueError,
                  "unsupported format character '%c' (0x%x) "
                  "at index %zd",
                  c, c,
                  (Py_ssize_t)(fmt - 1 - format));
                goto error;
            }

            if (sign) {
                if (*pbuf == '-' || *pbuf == '+') {
                    sign = *pbuf++;
                    len--;
                }
                else if (flags & F_SIGN)
                    sign = '+';
                else if (flags & F_BLANK)
                    sign = ' ';
                else
                    sign = 0;
            }
            if (width < len)
                width = len;

            alloc = width;
            if (sign != 0 && len == width)
                alloc++;
            /* 2: size preallocated for %s */
            if (alloc > 2) {
                res = _PyBytesWriter_Prepare(&writer, res, alloc - 2);
                if (res == NULL)
                    goto error;
            }
#ifdef Py_DEBUG
            before = res;
#endif

            /* Write the sign if needed */
            if (sign) {
                if (fill != ' ')
                    *res++ = sign;
                if (width > len)
                    width--;
            }

            /* Write the numeric prefix for "x", "X" and "o" formats
               if the alternate form is used.
               For example, write "0x" for the "%#x" format. */
            if ((flags & F_ALT) && (c == 'x' || c == 'X')) {
                assert(pbuf[0] == '0');
                assert(pbuf[1] == c);
                if (fill != ' ') {
                    *res++ = *pbuf++;
                    *res++ = *pbuf++;
                }
                width -= 2;
                if (width < 0)
                    width = 0;
                len -= 2;
            }

            /* Pad left with the fill character if needed */
            if (width > len && !(flags & F_LJUST)) {
                memset(res, fill, width - len);
                res += (width - len);
                width = len;
            }

            /* If padding with spaces: write sign if needed and/or numeric
               prefix if the alternate form is used */
            if (fill == ' ') {
                if (sign)